Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2807 insertions, 0 deletions

diff --git a/drivers/platform/surface/aggregator/controller.c b/drivers/platform/surface/aggregator/controller.c
new file mode 100644
index 000000000..30cea324f
--- /dev/null
+++ b/drivers/platform/surface/aggregator/controller.c
@@ -0,0 +1,2807 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Main SSAM/SSH controller structure and functionality.
+ *
+ * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/acpi.h>
+#include <linux/atomic.h>
+#include <linux/completion.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/kref.h>
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/lockdep.h>
+#include <linux/mutex.h>
+#include <linux/rculist.h>
+#include <linux/rbtree.h>
+#include <linux/rwsem.h>
+#include <linux/serdev.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/srcu.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/serial_hub.h>
+
+#include "controller.h"
+#include "ssh_msgb.h"
+#include "ssh_request_layer.h"
+
+#include "trace.h"
+
+
+/* -- Safe counters. -------------------------------------------------------- */
+
+/**
+ * ssh_seq_reset() - Reset/initialize sequence ID counter.
+ * @c: The counter to reset.
+ */
+static void ssh_seq_reset(struct ssh_seq_counter *c)
+{
+	WRITE_ONCE(c->value, 0);
+}
+
+/**
+ * ssh_seq_next() - Get next sequence ID.
+ * @c: The counter providing the sequence IDs.
+ *
+ * Return: Returns the next sequence ID of the counter.
+ */
+static u8 ssh_seq_next(struct ssh_seq_counter *c)
+{
+	u8 old = READ_ONCE(c->value);
+	u8 new = old + 1;
+	u8 ret;
+
+	while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
+		old = ret;
+		new = old + 1;
+	}
+
+	return old;
+}
+
+/**
+ * ssh_rqid_reset() - Reset/initialize request ID counter.
+ * @c: The counter to reset.
+ */
+static void ssh_rqid_reset(struct ssh_rqid_counter *c)
+{
+	WRITE_ONCE(c->value, 0);
+}
+
+/**
+ * ssh_rqid_next() - Get next request ID.
+ * @c: The counter providing the request IDs.
+ *
+ * Return: Returns the next request ID of the counter, skipping any reserved
+ * request IDs.
+ */
+static u16 ssh_rqid_next(struct ssh_rqid_counter *c)
+{
+	u16 old = READ_ONCE(c->value);
+	u16 new = ssh_rqid_next_valid(old);
+	u16 ret;
+
+	while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
+		old = ret;
+		new = ssh_rqid_next_valid(old);
+	}
+
+	return old;
+}
+
+
+/* -- Event notifier/callbacks. --------------------------------------------- */
+/*
+ * The notifier system is based on linux/notifier.h, specifically the SRCU
+ * implementation. The difference to that is, that some bits of the notifier
+ * call return value can be tracked across multiple calls. This is done so
+ * that handling of events can be tracked and a warning can be issued in case
+ * an event goes unhandled. The idea of that warning is that it should help
+ * discover and identify new/currently unimplemented features.
+ */
+
+/**
+ * ssam_event_matches_notifier() - Test if an event matches a notifier.
+ * @n: The event notifier to test against.
+ * @event: The event to test.
+ *
+ * Return: Returns %true if the given event matches the given notifier
+ * according to the rules set in the notifier's event mask, %false otherwise.
+ */
+static bool ssam_event_matches_notifier(const struct ssam_event_notifier *n,
+					const struct ssam_event *event)
+{
+	bool match = n->event.id.target_category == event->target_category;
+
+	if (n->event.mask & SSAM_EVENT_MASK_TARGET)
+		match &= n->event.reg.target_id == event->target_id;
+
+	if (n->event.mask & SSAM_EVENT_MASK_INSTANCE)
+		match &= n->event.id.instance == event->instance_id;
+
+	return match;
+}
+
+/**
+ * ssam_nfblk_call_chain() - Call event notifier callbacks of the given chain.
+ * @nh:    The notifier head for which the notifier callbacks should be called.
+ * @event: The event data provided to the callbacks.
+ *
+ * Call all registered notifier callbacks in order of their priority until
+ * either no notifier is left or a notifier returns a value with the
+ * %SSAM_NOTIF_STOP bit set. Note that this bit is automatically set via
+ * ssam_notifier_from_errno() on any non-zero error value.
+ *
+ * Return: Returns the notifier status value, which contains the notifier
+ * status bits (%SSAM_NOTIF_HANDLED and %SSAM_NOTIF_STOP) as well as a
+ * potential error value returned from the last executed notifier callback.
+ * Use ssam_notifier_to_errno() to convert this value to the original error
+ * value.
+ */
+static int ssam_nfblk_call_chain(struct ssam_nf_head *nh, struct ssam_event *event)
+{
+	struct ssam_event_notifier *nf;
+	int ret = 0, idx;
+
+	idx = srcu_read_lock(&nh->srcu);
+
+	list_for_each_entry_rcu(nf, &nh->head, base.node,
+				srcu_read_lock_held(&nh->srcu)) {
+		if (ssam_event_matches_notifier(nf, event)) {
+			ret = (ret & SSAM_NOTIF_STATE_MASK) | nf->base.fn(nf, event);
+			if (ret & SSAM_NOTIF_STOP)
+				break;
+		}
+	}
+
+	srcu_read_unlock(&nh->srcu, idx);
+	return ret;
+}
+
+/**
+ * ssam_nfblk_insert() - Insert a new notifier block into the given notifier
+ * list.
+ * @nh: The notifier head into which the block should be inserted.
+ * @nb: The notifier block to add.
+ *
+ * Note: This function must be synchronized by the caller with respect to other
+ * insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
+ *
+ * Return: Returns zero on success, %-EEXIST if the notifier block has already
+ * been registered.
+ */
+static int ssam_nfblk_insert(struct ssam_nf_head *nh, struct ssam_notifier_block *nb)
+{
+	struct ssam_notifier_block *p;
+	struct list_head *h;
+
+	/* Runs under lock, no need for RCU variant. */
+	list_for_each(h, &nh->head) {
+		p = list_entry(h, struct ssam_notifier_block, node);
+
+		if (unlikely(p == nb)) {
+			WARN(1, "double register detected");
+			return -EEXIST;
+		}
+
+		if (nb->priority > p->priority)
+			break;
+	}
+
+	list_add_tail_rcu(&nb->node, h);
+	return 0;
+}
+
+/**
+ * ssam_nfblk_find() - Check if a notifier block is registered on the given
+ * notifier head.
+ * list.
+ * @nh: The notifier head on which to search.
+ * @nb: The notifier block to search for.
+ *
+ * Note: This function must be synchronized by the caller with respect to other
+ * insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
+ *
+ * Return: Returns true if the given notifier block is registered on the given
+ * notifier head, false otherwise.
+ */
+static bool ssam_nfblk_find(struct ssam_nf_head *nh, struct ssam_notifier_block *nb)
+{
+	struct ssam_notifier_block *p;
+
+	/* Runs under lock, no need for RCU variant. */
+	list_for_each_entry(p, &nh->head, node) {
+		if (p == nb)
+			return true;
+	}
+
+	return false;
+}
+
+/**
+ * ssam_nfblk_remove() - Remove a notifier block from its notifier list.
+ * @nb: The notifier block to be removed.
+ *
+ * Note: This function must be synchronized by the caller with respect to
+ * other insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
+ * Furthermore, the caller _must_ ensure SRCU synchronization by calling
+ * synchronize_srcu() with ``nh->srcu`` after leaving the critical section, to
+ * ensure that the removed notifier block is not in use any more.
+ */
+static void ssam_nfblk_remove(struct ssam_notifier_block *nb)
+{
+	list_del_rcu(&nb->node);
+}
+
+/**
+ * ssam_nf_head_init() - Initialize the given notifier head.
+ * @nh: The notifier head to initialize.
+ */
+static int ssam_nf_head_init(struct ssam_nf_head *nh)
+{
+	int status;
+
+	status = init_srcu_struct(&nh->srcu);
+	if (status)
+		return status;
+
+	INIT_LIST_HEAD(&nh->head);
+	return 0;
+}
+
+/**
+ * ssam_nf_head_destroy() - Deinitialize the given notifier head.
+ * @nh: The notifier head to deinitialize.
+ */
+static void ssam_nf_head_destroy(struct ssam_nf_head *nh)
+{
+	cleanup_srcu_struct(&nh->srcu);
+}
+
+
+/* -- Event/notification registry. ------------------------------------------ */
+
+/**
+ * struct ssam_nf_refcount_key - Key used for event activation reference
+ * counting.
+ * @reg: The registry via which the event is enabled/disabled.
+ * @id:  The ID uniquely describing the event.
+ */
+struct ssam_nf_refcount_key {
+	struct ssam_event_registry reg;
+	struct ssam_event_id id;
+};
+
+/**
+ * struct ssam_nf_refcount_entry - RB-tree entry for reference counting event
+ * activations.
+ * @node:     The node of this entry in the rb-tree.
+ * @key:      The key of the event.
+ * @refcount: The reference-count of the event.
+ * @flags:    The flags used when enabling the event.
+ */
+struct ssam_nf_refcount_entry {
+	struct rb_node node;
+	struct ssam_nf_refcount_key key;
+	int refcount;
+	u8 flags;
+};
+
+/**
+ * ssam_nf_refcount_inc() - Increment reference-/activation-count of the given
+ * event.
+ * @nf:  The notifier system reference.
+ * @reg: The registry used to enable/disable the event.
+ * @id:  The event ID.
+ *
+ * Increments the reference-/activation-count associated with the specified
+ * event type/ID, allocating a new entry for this event ID if necessary. A
+ * newly allocated entry will have a refcount of one.
+ *
+ * Note: ``nf->lock`` must be held when calling this function.
+ *
+ * Return: Returns the refcount entry on success. Returns an error pointer
+ * with %-ENOSPC if there have already been %INT_MAX events of the specified
+ * ID and type registered, or %-ENOMEM if the entry could not be allocated.
+ */
+static struct ssam_nf_refcount_entry *
+ssam_nf_refcount_inc(struct ssam_nf *nf, struct ssam_event_registry reg,
+		     struct ssam_event_id id)
+{
+	struct ssam_nf_refcount_entry *entry;
+	struct ssam_nf_refcount_key key;
+	struct rb_node **link = &nf->refcount.rb_node;
+	struct rb_node *parent = NULL;
+	int cmp;
+
+	lockdep_assert_held(&nf->lock);
+
+	key.reg = reg;
+	key.id = id;
+
+	while (*link) {
+		entry = rb_entry(*link, struct ssam_nf_refcount_entry, node);
+		parent = *link;
+
+		cmp = memcmp(&key, &entry->key, sizeof(key));
+		if (cmp < 0) {
+			link = &(*link)->rb_left;
+		} else if (cmp > 0) {
+			link = &(*link)->rb_right;
+		} else if (entry->refcount < INT_MAX) {
+			entry->refcount++;
+			return entry;
+		} else {
+			WARN_ON(1);
+			return ERR_PTR(-ENOSPC);
+		}
+	}
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return ERR_PTR(-ENOMEM);
+
+	entry->key = key;
+	entry->refcount = 1;
+
+	rb_link_node(&entry->node, parent, link);
+	rb_insert_color(&entry->node, &nf->refcount);
+
+	return entry;
+}
+
+/**
+ * ssam_nf_refcount_dec() - Decrement reference-/activation-count of the given
+ * event.
+ * @nf:  The notifier system reference.
+ * @reg: The registry used to enable/disable the event.
+ * @id:  The event ID.
+ *
+ * Decrements the reference-/activation-count of the specified event,
+ * returning its entry. If the returned entry has a refcount of zero, the
+ * caller is responsible for freeing it using kfree().
+ *
+ * Note: ``nf->lock`` must be held when calling this function.
+ *
+ * Return: Returns the refcount entry on success or %NULL if the entry has not
+ * been found.
+ */
+static struct ssam_nf_refcount_entry *
+ssam_nf_refcount_dec(struct ssam_nf *nf, struct ssam_event_registry reg,
+		     struct ssam_event_id id)
+{
+	struct ssam_nf_refcount_entry *entry;
+	struct ssam_nf_refcount_key key;
+	struct rb_node *node = nf->refcount.rb_node;
+	int cmp;
+
+	lockdep_assert_held(&nf->lock);
+
+	key.reg = reg;
+	key.id = id;
+
+	while (node) {
+		entry = rb_entry(node, struct ssam_nf_refcount_entry, node);
+
+		cmp = memcmp(&key, &entry->key, sizeof(key));
+		if (cmp < 0) {
+			node = node->rb_left;
+		} else if (cmp > 0) {
+			node = node->rb_right;
+		} else {
+			entry->refcount--;
+			if (entry->refcount == 0)
+				rb_erase(&entry->node, &nf->refcount);
+
+			return entry;
+		}
+	}
+
+	return NULL;
+}
+
+/**
+ * ssam_nf_refcount_dec_free() - Decrement reference-/activation-count of the
+ * given event and free its entry if the reference count reaches zero.
+ * @nf:  The notifier system reference.
+ * @reg: The registry used to enable/disable the event.
+ * @id:  The event ID.
+ *
+ * Decrements the reference-/activation-count of the specified event, freeing
+ * its entry if it reaches zero.
+ *
+ * Note: ``nf->lock`` must be held when calling this function.
+ */
+static void ssam_nf_refcount_dec_free(struct ssam_nf *nf,
+				      struct ssam_event_registry reg,
+				      struct ssam_event_id id)
+{
+	struct ssam_nf_refcount_entry *entry;
+
+	lockdep_assert_held(&nf->lock);
+
+	entry = ssam_nf_refcount_dec(nf, reg, id);
+	if (entry && entry->refcount == 0)
+		kfree(entry);
+}
+
+/**
+ * ssam_nf_refcount_empty() - Test if the notification system has any
+ * enabled/active events.
+ * @nf: The notification system.
+ */
+static bool ssam_nf_refcount_empty(struct ssam_nf *nf)
+{
+	return RB_EMPTY_ROOT(&nf->refcount);
+}
+
+/**
+ * ssam_nf_call() - Call notification callbacks for the provided event.
+ * @nf:    The notifier system
+ * @dev:   The associated device, only used for logging.
+ * @rqid:  The request ID of the event.
+ * @event: The event provided to the callbacks.
+ *
+ * Execute registered callbacks in order of their priority until either no
+ * callback is left or a callback returns a value with the %SSAM_NOTIF_STOP
+ * bit set. Note that this bit is set automatically when converting non-zero
+ * error values via ssam_notifier_from_errno() to notifier values.
+ *
+ * Also note that any callback that could handle an event should return a value
+ * with bit %SSAM_NOTIF_HANDLED set, indicating that the event does not go
+ * unhandled/ignored. In case no registered callback could handle an event,
+ * this function will emit a warning.
+ *
+ * In case a callback failed, this function will emit an error message.
+ */
+static void ssam_nf_call(struct ssam_nf *nf, struct device *dev, u16 rqid,
+			 struct ssam_event *event)
+{
+	struct ssam_nf_head *nf_head;
+	int status, nf_ret;
+
+	if (!ssh_rqid_is_event(rqid)) {
+		dev_warn(dev, "event: unsupported rqid: %#06x\n", rqid);
+		return;
+	}
+
+	nf_head = &nf->head[ssh_rqid_to_event(rqid)];
+	nf_ret = ssam_nfblk_call_chain(nf_head, event);
+	status = ssam_notifier_to_errno(nf_ret);
+
+	if (status < 0) {
+		dev_err(dev,
+			"event: error handling event: %d (tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
+			status, event->target_category, event->target_id,
+			event->command_id, event->instance_id);
+	} else if (!(nf_ret & SSAM_NOTIF_HANDLED)) {
+		dev_warn(dev,
+			 "event: unhandled event (rqid: %#04x, tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
+			 rqid, event->target_category, event->target_id,
+			 event->command_id, event->instance_id);
+	}
+}
+
+/**
+ * ssam_nf_init() - Initialize the notifier system.
+ * @nf: The notifier system to initialize.
+ */
+static int ssam_nf_init(struct ssam_nf *nf)
+{
+	int i, status;
+
+	for (i = 0; i < SSH_NUM_EVENTS; i++) {
+		status = ssam_nf_head_init(&nf->head[i]);
+		if (status)
+			break;
+	}
+
+	if (status) {
+		while (i--)
+			ssam_nf_head_destroy(&nf->head[i]);
+
+		return status;
+	}
+
+	mutex_init(&nf->lock);
+	return 0;
+}
+
+/**
+ * ssam_nf_destroy() - Deinitialize the notifier system.
+ * @nf: The notifier system to deinitialize.
+ */
+static void ssam_nf_destroy(struct ssam_nf *nf)
+{
+	int i;
+
+	for (i = 0; i < SSH_NUM_EVENTS; i++)
+		ssam_nf_head_destroy(&nf->head[i]);
+
+	mutex_destroy(&nf->lock);
+}
+
+
+/* -- Event/async request completion system. -------------------------------- */
+
+#define SSAM_CPLT_WQ_NAME	"ssam_cpltq"
+
+/*
+ * SSAM_CPLT_WQ_BATCH - Maximum number of event item completions executed per
+ * work execution. Used to prevent livelocking of the workqueue. Value chosen
+ * via educated guess, may be adjusted.
+ */
+#define SSAM_CPLT_WQ_BATCH	10
+
+/*
+ * SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN - Maximum payload length for a cached
+ * &struct ssam_event_item.
+ *
+ * This length has been chosen to be accommodate standard touchpad and
+ * keyboard input events. Events with larger payloads will be allocated
+ * separately.
+ */
+#define SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN	32
+
+static struct kmem_cache *ssam_event_item_cache;
+
+/**
+ * ssam_event_item_cache_init() - Initialize the event item cache.
+ */
+int ssam_event_item_cache_init(void)
+{
+	const unsigned int size = sizeof(struct ssam_event_item)
+				  + SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN;
+	const unsigned int align = __alignof__(struct ssam_event_item);
+	struct kmem_cache *cache;
+
+	cache = kmem_cache_create("ssam_event_item", size, align, 0, NULL);
+	if (!cache)
+		return -ENOMEM;
+
+	ssam_event_item_cache = cache;
+	return 0;
+}
+
+/**
+ * ssam_event_item_cache_destroy() - Deinitialize the event item cache.
+ */
+void ssam_event_item_cache_destroy(void)
+{
+	kmem_cache_destroy(ssam_event_item_cache);
+	ssam_event_item_cache = NULL;
+}
+
+static void __ssam_event_item_free_cached(struct ssam_event_item *item)
+{
+	kmem_cache_free(ssam_event_item_cache, item);
+}
+
+static void __ssam_event_item_free_generic(struct ssam_event_item *item)
+{
+	kfree(item);
+}
+
+/**
+ * ssam_event_item_free() - Free the provided event item.
+ * @item: The event item to free.
+ */
+static void ssam_event_item_free(struct ssam_event_item *item)
+{
+	trace_ssam_event_item_free(item);
+	item->ops.free(item);
+}
+
+/**
+ * ssam_event_item_alloc() - Allocate an event item with the given payload size.
+ * @len:   The event payload length.
+ * @flags: The flags used for allocation.
+ *
+ * Allocate an event item with the given payload size, preferring allocation
+ * from the event item cache if the payload is small enough (i.e. smaller than
+ * %SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN). Sets the item operations and payload
+ * length values. The item free callback (``ops.free``) should not be
+ * overwritten after this call.
+ *
+ * Return: Returns the newly allocated event item.
+ */
+static struct ssam_event_item *ssam_event_item_alloc(size_t len, gfp_t flags)
+{
+	struct ssam_event_item *item;
+
+	if (len <= SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN) {
+		item = kmem_cache_alloc(ssam_event_item_cache, flags);
+		if (!item)
+			return NULL;
+
+		item->ops.free = __ssam_event_item_free_cached;
+	} else {
+		item = kzalloc(struct_size(item, event.data, len), flags);
+		if (!item)
+			return NULL;
+
+		item->ops.free = __ssam_event_item_free_generic;
+	}
+
+	item->event.length = len;
+
+	trace_ssam_event_item_alloc(item, len);
+	return item;
+}
+
+/**
+ * ssam_event_queue_push() - Push an event item to the event queue.
+ * @q:    The event queue.
+ * @item: The item to add.
+ */
+static void ssam_event_queue_push(struct ssam_event_queue *q,
+				  struct ssam_event_item *item)
+{
+	spin_lock(&q->lock);
+	list_add_tail(&item->node, &q->head);
+	spin_unlock(&q->lock);
+}
+
+/**
+ * ssam_event_queue_pop() - Pop the next event item from the event queue.
+ * @q: The event queue.
+ *
+ * Returns and removes the next event item from the queue. Returns %NULL If
+ * there is no event item left.
+ */
+static struct ssam_event_item *ssam_event_queue_pop(struct ssam_event_queue *q)
+{
+	struct ssam_event_item *item;
+
+	spin_lock(&q->lock);
+	item = list_first_entry_or_null(&q->head, struct ssam_event_item, node);
+	if (item)
+		list_del(&item->node);
+	spin_unlock(&q->lock);
+
+	return item;
+}
+
+/**
+ * ssam_event_queue_is_empty() - Check if the event queue is empty.
+ * @q: The event queue.
+ */
+static bool ssam_event_queue_is_empty(struct ssam_event_queue *q)
+{
+	bool empty;
+
+	spin_lock(&q->lock);
+	empty = list_empty(&q->head);
+	spin_unlock(&q->lock);
+
+	return empty;
+}
+
+/**
+ * ssam_cplt_get_event_queue() - Get the event queue for the given parameters.
+ * @cplt: The completion system on which to look for the queue.
+ * @tid:  The target ID of the queue.
+ * @rqid: The request ID representing the event ID for which to get the queue.
+ *
+ * Return: Returns the event queue corresponding to the event type described
+ * by the given parameters. If the request ID does not represent an event,
+ * this function returns %NULL. If the target ID is not supported, this
+ * function will fall back to the default target ID (``tid = 1``).
+ */
+static
+struct ssam_event_queue *ssam_cplt_get_event_queue(struct ssam_cplt *cplt,
+						   u8 tid, u16 rqid)
+{
+	u16 event = ssh_rqid_to_event(rqid);
+	u16 tidx = ssh_tid_to_index(tid);
+
+	if (!ssh_rqid_is_event(rqid)) {
+		dev_err(cplt->dev, "event: unsupported request ID: %#06x\n", rqid);
+		return NULL;
+	}
+
+	if (!ssh_tid_is_valid(tid)) {
+		dev_warn(cplt->dev, "event: unsupported target ID: %u\n", tid);
+		tidx = 0;
+	}
+
+	return &cplt->event.target[tidx].queue[event];
+}
+
+/**
+ * ssam_cplt_submit() - Submit a work item to the completion system workqueue.
+ * @cplt: The completion system.
+ * @work: The work item to submit.
+ */
+static bool ssam_cplt_submit(struct ssam_cplt *cplt, struct work_struct *work)
+{
+	return queue_work(cplt->wq, work);
+}
+
+/**
+ * ssam_cplt_submit_event() - Submit an event to the completion system.
+ * @cplt: The completion system.
+ * @item: The event item to submit.
+ *
+ * Submits the event to the completion system by queuing it on the event item
+ * queue and queuing the respective event queue work item on the completion
+ * workqueue, which will eventually complete the event.
+ *
+ * Return: Returns zero on success, %-EINVAL if there is no event queue that
+ * can handle the given event item.
+ */
+static int ssam_cplt_submit_event(struct ssam_cplt *cplt,
+				  struct ssam_event_item *item)
+{
+	struct ssam_event_queue *evq;
+
+	evq = ssam_cplt_get_event_queue(cplt, item->event.target_id, item->rqid);
+	if (!evq)
+		return -EINVAL;
+
+	ssam_event_queue_push(evq, item);
+	ssam_cplt_submit(cplt, &evq->work);
+	return 0;
+}
+
+/**
+ * ssam_cplt_flush() - Flush the completion system.
+ * @cplt: The completion system.
+ *
+ * Flush the completion system by waiting until all currently submitted work
+ * items have been completed.
+ *
+ * Note: This function does not guarantee that all events will have been
+ * handled once this call terminates. In case of a larger number of
+ * to-be-completed events, the event queue work function may re-schedule its
+ * work item, which this flush operation will ignore.
+ *
+ * This operation is only intended to, during normal operation prior to
+ * shutdown, try to complete most events and requests to get them out of the
+ * system while the system is still fully operational. It does not aim to
+ * provide any guarantee that all of them have been handled.
+ */
+static void ssam_cplt_flush(struct ssam_cplt *cplt)
+{
+	flush_workqueue(cplt->wq);
+}
+
+static void ssam_event_queue_work_fn(struct work_struct *work)
+{
+	struct ssam_event_queue *queue;
+	struct ssam_event_item *item;
+	struct ssam_nf *nf;
+	struct device *dev;
+	unsigned int iterations = SSAM_CPLT_WQ_BATCH;
+
+	queue = container_of(work, struct ssam_event_queue, work);
+	nf = &queue->cplt->event.notif;
+	dev = queue->cplt->dev;
+
+	/* Limit number of processed events to avoid livelocking. */
+	do {
+		item = ssam_event_queue_pop(queue);
+		if (!item)
+			return;
+
+		ssam_nf_call(nf, dev, item->rqid, &item->event);
+		ssam_event_item_free(item);
+	} while (--iterations);
+
+	if (!ssam_event_queue_is_empty(queue))
+		ssam_cplt_submit(queue->cplt, &queue->work);
+}
+
+/**
+ * ssam_event_queue_init() - Initialize an event queue.
+ * @cplt: The completion system on which the queue resides.
+ * @evq:  The event queue to initialize.
+ */
+static void ssam_event_queue_init(struct ssam_cplt *cplt,
+				  struct ssam_event_queue *evq)
+{
+	evq->cplt = cplt;
+	spin_lock_init(&evq->lock);
+	INIT_LIST_HEAD(&evq->head);
+	INIT_WORK(&evq->work, ssam_event_queue_work_fn);
+}
+
+/**
+ * ssam_cplt_init() - Initialize completion system.
+ * @cplt: The completion system to initialize.
+ * @dev:  The device used for logging.
+ */
+static int ssam_cplt_init(struct ssam_cplt *cplt, struct device *dev)
+{
+	struct ssam_event_target *target;
+	int status, c, i;
+
+	cplt->dev = dev;
+
+	cplt->wq = alloc_workqueue(SSAM_CPLT_WQ_NAME, WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
+	if (!cplt->wq)
+		return -ENOMEM;
+
+	for (c = 0; c < ARRAY_SIZE(cplt->event.target); c++) {
+		target = &cplt->event.target[c];
+
+		for (i = 0; i < ARRAY_SIZE(target->queue); i++)
+			ssam_event_queue_init(cplt, &target->queue[i]);
+	}
+
+	status = ssam_nf_init(&cplt->event.notif);
+	if (status)
+		destroy_workqueue(cplt->wq);
+
+	return status;
+}
+
+/**
+ * ssam_cplt_destroy() - Deinitialize the completion system.
+ * @cplt: The completion system to deinitialize.
+ *
+ * Deinitialize the given completion system and ensure that all pending, i.e.
+ * yet-to-be-completed, event items and requests have been handled.
+ */
+static void ssam_cplt_destroy(struct ssam_cplt *cplt)
+{
+	/*
+	 * Note: destroy_workqueue ensures that all currently queued work will
+	 * be fully completed and the workqueue drained. This means that this
+	 * call will inherently also free any queued ssam_event_items, thus we
+	 * don't have to take care of that here explicitly.
+	 */
+	destroy_workqueue(cplt->wq);
+	ssam_nf_destroy(&cplt->event.notif);
+}
+
+
+/* -- Main SSAM device structures. ------------------------------------------ */
+
+/**
+ * ssam_controller_device() - Get the &struct device associated with this
+ * controller.
+ * @c: The controller for which to get the device.
+ *
+ * Return: Returns the &struct device associated with this controller,
+ * providing its lower-level transport.
+ */
+struct device *ssam_controller_device(struct ssam_controller *c)
+{
+	return ssh_rtl_get_device(&c->rtl);
+}
+EXPORT_SYMBOL_GPL(ssam_controller_device);
+
+static void __ssam_controller_release(struct kref *kref)
+{
+	struct ssam_controller *ctrl = to_ssam_controller(kref, kref);
+
+	/*
+	 * The lock-call here is to satisfy lockdep. At this point we really
+	 * expect this to be the last remaining reference to the controller.
+	 * Anything else is a bug.
+	 */
+	ssam_controller_lock(ctrl);
+	ssam_controller_destroy(ctrl);
+	ssam_controller_unlock(ctrl);
+
+	kfree(ctrl);
+}
+
+/**
+ * ssam_controller_get() - Increment reference count of controller.
+ * @c: The controller.
+ *
+ * Return: Returns the controller provided as input.
+ */
+struct ssam_controller *ssam_controller_get(struct ssam_controller *c)
+{
+	if (c)
+		kref_get(&c->kref);
+	return c;
+}
+EXPORT_SYMBOL_GPL(ssam_controller_get);
+
+/**
+ * ssam_controller_put() - Decrement reference count of controller.
+ * @c: The controller.
+ */
+void ssam_controller_put(struct ssam_controller *c)
+{
+	if (c)
+		kref_put(&c->kref, __ssam_controller_release);
+}
+EXPORT_SYMBOL_GPL(ssam_controller_put);
+
+/**
+ * ssam_controller_statelock() - Lock the controller against state transitions.
+ * @c: The controller to lock.
+ *
+ * Lock the controller against state transitions. Holding this lock guarantees
+ * that the controller will not transition between states, i.e. if the
+ * controller is in state "started", when this lock has been acquired, it will
+ * remain in this state at least until the lock has been released.
+ *
+ * Multiple clients may concurrently hold this lock. In other words: The
+ * ``statelock`` functions represent the read-lock part of a r/w-semaphore.
+ * Actions causing state transitions of the controller must be executed while
+ * holding the write-part of this r/w-semaphore (see ssam_controller_lock()
+ * and ssam_controller_unlock() for that).
+ *
+ * See ssam_controller_stateunlock() for the corresponding unlock function.
+ */
+void ssam_controller_statelock(struct ssam_controller *c)
+{
+	down_read(&c->lock);
+}
+EXPORT_SYMBOL_GPL(ssam_controller_statelock);
+
+/**
+ * ssam_controller_stateunlock() - Unlock controller state transitions.
+ * @c: The controller to unlock.
+ *
+ * See ssam_controller_statelock() for the corresponding lock function.
+ */
+void ssam_controller_stateunlock(struct ssam_controller *c)
+{
+	up_read(&c->lock);
+}
+EXPORT_SYMBOL_GPL(ssam_controller_stateunlock);
+
+/**
+ * ssam_controller_lock() - Acquire the main controller lock.
+ * @c: The controller to lock.
+ *
+ * This lock must be held for any state transitions, including transition to
+ * suspend/resumed states and during shutdown. See ssam_controller_statelock()
+ * for more details on controller locking.
+ *
+ * See ssam_controller_unlock() for the corresponding unlock function.
+ */
+void ssam_controller_lock(struct ssam_controller *c)
+{
+	down_write(&c->lock);
+}
+
+/*
+ * ssam_controller_unlock() - Release the main controller lock.
+ * @c: The controller to unlock.
+ *
+ * See ssam_controller_lock() for the corresponding lock function.
+ */
+void ssam_controller_unlock(struct ssam_controller *c)
+{
+	up_write(&c->lock);
+}
+
+static void ssam_handle_event(struct ssh_rtl *rtl,
+			      const struct ssh_command *cmd,
+			      const struct ssam_span *data)
+{
+	struct ssam_controller *ctrl = to_ssam_controller(rtl, rtl);
+	struct ssam_event_item *item;
+
+	item = ssam_event_item_alloc(data->len, GFP_KERNEL);
+	if (!item)
+		return;
+
+	item->rqid = get_unaligned_le16(&cmd->rqid);
+	item->event.target_category = cmd->tc;
+	item->event.target_id = cmd->tid_in;
+	item->event.command_id = cmd->cid;
+	item->event.instance_id = cmd->iid;
+	memcpy(&item->event.data[0], data->ptr, data->len);
+
+	if (WARN_ON(ssam_cplt_submit_event(&ctrl->cplt, item)))
+		ssam_event_item_free(item);
+}
+
+static const struct ssh_rtl_ops ssam_rtl_ops = {
+	.handle_event = ssam_handle_event,
+};
+
+static bool ssam_notifier_is_empty(struct ssam_controller *ctrl);
+static void ssam_notifier_unregister_all(struct ssam_controller *ctrl);
+
+#define SSAM_SSH_DSM_REVISION	0
+
+/* d5e383e1-d892-4a76-89fc-f6aaae7ed5b5 */
+static const guid_t SSAM_SSH_DSM_GUID =
+	GUID_INIT(0xd5e383e1, 0xd892, 0x4a76,
+		  0x89, 0xfc, 0xf6, 0xaa, 0xae, 0x7e, 0xd5, 0xb5);
+
+enum ssh_dsm_fn {
+	SSH_DSM_FN_SSH_POWER_PROFILE             = 0x05,
+	SSH_DSM_FN_SCREEN_ON_SLEEP_IDLE_TIMEOUT  = 0x06,
+	SSH_DSM_FN_SCREEN_OFF_SLEEP_IDLE_TIMEOUT = 0x07,
+	SSH_DSM_FN_D3_CLOSES_HANDLE              = 0x08,
+	SSH_DSM_FN_SSH_BUFFER_SIZE               = 0x09,
+};
+
+static int ssam_dsm_get_functions(acpi_handle handle, u64 *funcs)
+{
+	union acpi_object *obj;
+	u64 mask = 0;
+	int i;
+
+	*funcs = 0;
+
+	/*
+	 * The _DSM function is only present on newer models. It is not
+	 * present on 5th and 6th generation devices (i.e. up to and including
+	 * Surface Pro 6, Surface Laptop 2, Surface Book 2).
+	 *
+	 * If the _DSM is not present, indicate that no function is supported.
+	 * This will result in default values being set.
+	 */
+	if (!acpi_has_method(handle, "_DSM"))
+		return 0;
+
+	obj = acpi_evaluate_dsm_typed(handle, &SSAM_SSH_DSM_GUID,
+				      SSAM_SSH_DSM_REVISION, 0, NULL,
+				      ACPI_TYPE_BUFFER);
+	if (!obj)
+		return -EIO;
+
+	for (i = 0; i < obj->buffer.length && i < 8; i++)
+		mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));
+
+	if (mask & BIT(0))
+		*funcs = mask;
+
+	ACPI_FREE(obj);
+	return 0;
+}
+
+static int ssam_dsm_load_u32(acpi_handle handle, u64 funcs, u64 func, u32 *ret)
+{
+	union acpi_object *obj;
+	u64 val;
+
+	if (!(funcs & BIT_ULL(func)))
+		return 0; /* Not supported, leave *ret at its default value */
+
+	obj = acpi_evaluate_dsm_typed(handle, &SSAM_SSH_DSM_GUID,
+				      SSAM_SSH_DSM_REVISION, func, NULL,
+				      ACPI_TYPE_INTEGER);
+	if (!obj)
+		return -EIO;
+
+	val = obj->integer.value;
+	ACPI_FREE(obj);
+
+	if (val > U32_MAX)
+		return -ERANGE;
+
+	*ret = val;
+	return 0;
+}
+
+/**
+ * ssam_controller_caps_load_from_acpi() - Load controller capabilities from
+ * ACPI _DSM.
+ * @handle: The handle of the ACPI controller/SSH device.
+ * @caps:   Where to store the capabilities in.
+ *
+ * Initializes the given controller capabilities with default values, then
+ * checks and, if the respective _DSM functions are available, loads the
+ * actual capabilities from the _DSM.
+ *
+ * Return: Returns zero on success, a negative error code on failure.
+ */
+static
+int ssam_controller_caps_load_from_acpi(acpi_handle handle,
+					struct ssam_controller_caps *caps)
+{
+	u32 d3_closes_handle = false;
+	u64 funcs;
+	int status;
+
+	/* Set defaults. */
+	caps->ssh_power_profile = U32_MAX;
+	caps->screen_on_sleep_idle_timeout = U32_MAX;
+	caps->screen_off_sleep_idle_timeout = U32_MAX;
+	caps->d3_closes_handle = false;
+	caps->ssh_buffer_size = U32_MAX;
+
+	/* Pre-load supported DSM functions. */
+	status = ssam_dsm_get_functions(handle, &funcs);
+	if (status)
+		return status;
+
+	/* Load actual values from ACPI, if present. */
+	status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_SSH_POWER_PROFILE,
+				   &caps->ssh_power_profile);
+	if (status)
+		return status;
+
+	status = ssam_dsm_load_u32(handle, funcs,
+				   SSH_DSM_FN_SCREEN_ON_SLEEP_IDLE_TIMEOUT,
+				   &caps->screen_on_sleep_idle_timeout);
+	if (status)
+		return status;
+
+	status = ssam_dsm_load_u32(handle, funcs,
+				   SSH_DSM_FN_SCREEN_OFF_SLEEP_IDLE_TIMEOUT,
+				   &caps->screen_off_sleep_idle_timeout);
+	if (status)
+		return status;
+
+	status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_D3_CLOSES_HANDLE,
+				   &d3_closes_handle);
+	if (status)
+		return status;
+
+	caps->d3_closes_handle = !!d3_closes_handle;
+
+	status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_SSH_BUFFER_SIZE,
+				   &caps->ssh_buffer_size);
+	if (status)
+		return status;
+
+	return 0;
+}
+
+/**
+ * ssam_controller_init() - Initialize SSAM controller.
+ * @ctrl:   The controller to initialize.
+ * @serdev: The serial device representing the underlying data transport.
+ *
+ * Initializes the given controller. Does neither start receiver nor
+ * transmitter threads. After this call, the controller has to be hooked up to
+ * the serdev core separately via &struct serdev_device_ops, relaying calls to
+ * ssam_controller_receive_buf() and ssam_controller_write_wakeup(). Once the
+ * controller has been hooked up, transmitter and receiver threads may be
+ * started via ssam_controller_start(). These setup steps need to be completed
+ * before controller can be used for requests.
+ */
+int ssam_controller_init(struct ssam_controller *ctrl,
+			 struct serdev_device *serdev)
+{
+	acpi_handle handle = ACPI_HANDLE(&serdev->dev);
+	int status;
+
+	init_rwsem(&ctrl->lock);
+	kref_init(&ctrl->kref);
+
+	status = ssam_controller_caps_load_from_acpi(handle, &ctrl->caps);
+	if (status)
+		return status;
+
+	dev_dbg(&serdev->dev,
+		"device capabilities:\n"
+		"  ssh_power_profile:             %u\n"
+		"  ssh_buffer_size:               %u\n"
+		"  screen_on_sleep_idle_timeout:  %u\n"
+		"  screen_off_sleep_idle_timeout: %u\n"
+		"  d3_closes_handle:              %u\n",
+		ctrl->caps.ssh_power_profile,
+		ctrl->caps.ssh_buffer_size,
+		ctrl->caps.screen_on_sleep_idle_timeout,
+		ctrl->caps.screen_off_sleep_idle_timeout,
+		ctrl->caps.d3_closes_handle);
+
+	ssh_seq_reset(&ctrl->counter.seq);
+	ssh_rqid_reset(&ctrl->counter.rqid);
+
+	/* Initialize event/request completion system. */
+	status = ssam_cplt_init(&ctrl->cplt, &serdev->dev);
+	if (status)
+		return status;
+
+	/* Initialize request and packet transport layers. */
+	status = ssh_rtl_init(&ctrl->rtl, serdev, &ssam_rtl_ops);
+	if (status) {
+		ssam_cplt_destroy(&ctrl->cplt);
+		return status;
+	}
+
+	/*
+	 * Set state via write_once even though we expect to be in an
+	 * exclusive context, due to smoke-testing in
+	 * ssam_request_sync_submit().
+	 */
+	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_INITIALIZED);
+	return 0;
+}
+
+/**
+ * ssam_controller_start() - Start the receiver and transmitter threads of the
+ * controller.
+ * @ctrl: The controller.
+ *
+ * Note: When this function is called, the controller should be properly
+ * hooked up to the serdev core via &struct serdev_device_ops. Please refer
+ * to ssam_controller_init() for more details on controller initialization.
+ *
+ * This function must be called with the main controller lock held (i.e. by
+ * calling ssam_controller_lock()).
+ */
+int ssam_controller_start(struct ssam_controller *ctrl)
+{
+	int status;
+
+	lockdep_assert_held_write(&ctrl->lock);
+
+	if (ctrl->state != SSAM_CONTROLLER_INITIALIZED)
+		return -EINVAL;
+
+	status = ssh_rtl_start(&ctrl->rtl);
+	if (status)
+		return status;
+
+	/*
+	 * Set state via write_once even though we expect to be locked/in an
+	 * exclusive context, due to smoke-testing in
+	 * ssam_request_sync_submit().
+	 */
+	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STARTED);
+	return 0;
+}
+
+/*
+ * SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT - Timeout for flushing requests during
+ * shutdown.
+ *
+ * Chosen to be larger than one full request timeout, including packets timing
+ * out. This value should give ample time to complete any outstanding requests
+ * during normal operation and account for the odd package timeout.
+ */
+#define SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT	msecs_to_jiffies(5000)
+
+/**
+ * ssam_controller_shutdown() - Shut down the controller.
+ * @ctrl: The controller.
+ *
+ * Shuts down the controller by flushing all pending requests and stopping the
+ * transmitter and receiver threads. All requests submitted after this call
+ * will fail with %-ESHUTDOWN. While it is discouraged to do so, this function
+ * is safe to use in parallel with ongoing request submission.
+ *
+ * In the course of this shutdown procedure, all currently registered
+ * notifiers will be unregistered. It is, however, strongly recommended to not
+ * rely on this behavior, and instead the party registering the notifier
+ * should unregister it before the controller gets shut down, e.g. via the
+ * SSAM bus which guarantees client devices to be removed before a shutdown.
+ *
+ * Note that events may still be pending after this call, but, due to the
+ * notifiers being unregistered, these events will be dropped when the
+ * controller is subsequently destroyed via ssam_controller_destroy().
+ *
+ * This function must be called with the main controller lock held (i.e. by
+ * calling ssam_controller_lock()).
+ */
+void ssam_controller_shutdown(struct ssam_controller *ctrl)
+{
+	enum ssam_controller_state s = ctrl->state;
+	int status;
+
+	lockdep_assert_held_write(&ctrl->lock);
+
+	if (s == SSAM_CONTROLLER_UNINITIALIZED || s == SSAM_CONTROLLER_STOPPED)
+		return;
+
+	/*
+	 * Try to flush pending events and requests while everything still
+	 * works. Note: There may still be packets and/or requests in the
+	 * system after this call (e.g. via control packets submitted by the
+	 * packet transport layer or flush timeout / failure, ...). Those will
+	 * be handled with the ssh_rtl_shutdown() call below.
+	 */
+	status = ssh_rtl_flush(&ctrl->rtl, SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT);
+	if (status) {
+		ssam_err(ctrl, "failed to flush request transport layer: %d\n",
+			 status);
+	}
+
+	/* Try to flush all currently completing requests and events. */
+	ssam_cplt_flush(&ctrl->cplt);
+
+	/*
+	 * We expect all notifiers to have been removed by the respective client
+	 * driver that set them up at this point. If this warning occurs, some
+	 * client driver has not done that...
+	 */
+	WARN_ON(!ssam_notifier_is_empty(ctrl));
+
+	/*
+	 * Nevertheless, we should still take care of drivers that don't behave
+	 * well. Thus disable all enabled events, unregister all notifiers.
+	 */
+	ssam_notifier_unregister_all(ctrl);
+
+	/*
+	 * Cancel remaining requests. Ensure no new ones can be queued and stop
+	 * threads.
+	 */
+	ssh_rtl_shutdown(&ctrl->rtl);
+
+	/*
+	 * Set state via write_once even though we expect to be locked/in an
+	 * exclusive context, due to smoke-testing in
+	 * ssam_request_sync_submit().
+	 */
+	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STOPPED);
+	ctrl->rtl.ptl.serdev = NULL;
+}
+
+/**
+ * ssam_controller_destroy() - Destroy the controller and free its resources.
+ * @ctrl: The controller.
+ *
+ * Ensures that all resources associated with the controller get freed. This
+ * function should only be called after the controller has been stopped via
+ * ssam_controller_shutdown(). In general, this function should not be called
+ * directly. The only valid place to call this function directly is during
+ * initialization, before the controller has been fully initialized and passed
+ * to other processes. This function is called automatically when the
+ * reference count of the controller reaches zero.
+ *
+ * This function must be called with the main controller lock held (i.e. by
+ * calling ssam_controller_lock()).
+ */
+void ssam_controller_destroy(struct ssam_controller *ctrl)
+{
+	lockdep_assert_held_write(&ctrl->lock);
+
+	if (ctrl->state == SSAM_CONTROLLER_UNINITIALIZED)
+		return;
+
+	WARN_ON(ctrl->state != SSAM_CONTROLLER_STOPPED);
+
+	/*
+	 * Note: New events could still have been received after the previous
+	 * flush in ssam_controller_shutdown, before the request transport layer
+	 * has been shut down. At this point, after the shutdown, we can be sure
+	 * that no new events will be queued. The call to ssam_cplt_destroy will
+	 * ensure that those remaining are being completed and freed.
+	 */
+
+	/* Actually free resources. */
+	ssam_cplt_destroy(&ctrl->cplt);
+	ssh_rtl_destroy(&ctrl->rtl);
+
+	/*
+	 * Set state via write_once even though we expect to be locked/in an
+	 * exclusive context, due to smoke-testing in
+	 * ssam_request_sync_submit().
+	 */
+	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_UNINITIALIZED);
+}
+
+/**
+ * ssam_controller_suspend() - Suspend the controller.
+ * @ctrl: The controller to suspend.
+ *
+ * Marks the controller as suspended. Note that display-off and D0-exit
+ * notifications have to be sent manually before transitioning the controller
+ * into the suspended state via this function.
+ *
+ * See ssam_controller_resume() for the corresponding resume function.
+ *
+ * Return: Returns %-EINVAL if the controller is currently not in the
+ * "started" state.
+ */
+int ssam_controller_suspend(struct ssam_controller *ctrl)
+{
+	ssam_controller_lock(ctrl);
+
+	if (ctrl->state != SSAM_CONTROLLER_STARTED) {
+		ssam_controller_unlock(ctrl);
+		return -EINVAL;
+	}
+
+	ssam_dbg(ctrl, "pm: suspending controller\n");
+
+	/*
+	 * Set state via write_once even though we're locked, due to
+	 * smoke-testing in ssam_request_sync_submit().
+	 */
+	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_SUSPENDED);
+
+	ssam_controller_unlock(ctrl);
+	return 0;
+}
+
+/**
+ * ssam_controller_resume() - Resume the controller from suspend.
+ * @ctrl: The controller to resume.
+ *
+ * Resume the controller from the suspended state it was put into via
+ * ssam_controller_suspend(). This function does not issue display-on and
+ * D0-entry notifications. If required, those have to be sent manually after
+ * this call.
+ *
+ * Return: Returns %-EINVAL if the controller is currently not suspended.
+ */
+int ssam_controller_resume(struct ssam_controller *ctrl)
+{
+	ssam_controller_lock(ctrl);
+
+	if (ctrl->state != SSAM_CONTROLLER_SUSPENDED) {
+		ssam_controller_unlock(ctrl);
+		return -EINVAL;
+	}
+
+	ssam_dbg(ctrl, "pm: resuming controller\n");
+
+	/*
+	 * Set state via write_once even though we're locked, due to
+	 * smoke-testing in ssam_request_sync_submit().
+	 */
+	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STARTED);
+
+	ssam_controller_unlock(ctrl);
+	return 0;
+}
+
+
+/* -- Top-level request interface ------------------------------------------- */
+
+/**
+ * ssam_request_write_data() - Construct and write SAM request message to
+ * buffer.
+ * @buf:  The buffer to write the data to.
+ * @ctrl: The controller via which the request will be sent.
+ * @spec: The request data and specification.
+ *
+ * Constructs a SAM/SSH request message and writes it to the provided buffer.
+ * The request and transport counters, specifically RQID and SEQ, will be set
+ * in this call. These counters are obtained from the controller. It is thus
+ * only valid to send the resulting message via the controller specified here.
+ *
+ * For calculation of the required buffer size, refer to the
+ * SSH_COMMAND_MESSAGE_LENGTH() macro.
+ *
+ * Return: Returns the number of bytes used in the buffer on success. Returns
+ * %-EINVAL if the payload length provided in the request specification is too
+ * large (larger than %SSH_COMMAND_MAX_PAYLOAD_SIZE) or if the provided buffer
+ * is too small.
+ */
+ssize_t ssam_request_write_data(struct ssam_span *buf,
+				struct ssam_controller *ctrl,
+				const struct ssam_request *spec)
+{
+	struct msgbuf msgb;
+	u16 rqid;
+	u8 seq;
+
+	if (spec->length > SSH_COMMAND_MAX_PAYLOAD_SIZE)
+		return -EINVAL;
+
+	if (SSH_COMMAND_MESSAGE_LENGTH(spec->length) > buf->len)
+		return -EINVAL;
+
+	msgb_init(&msgb, buf->ptr, buf->len);
+	seq = ssh_seq_next(&ctrl->counter.seq);
+	rqid = ssh_rqid_next(&ctrl->counter.rqid);
+	msgb_push_cmd(&msgb, seq, rqid, spec);
+
+	return msgb_bytes_used(&msgb);
+}
+EXPORT_SYMBOL_GPL(ssam_request_write_data);
+
+static void ssam_request_sync_complete(struct ssh_request *rqst,
+				       const struct ssh_command *cmd,
+				       const struct ssam_span *data, int status)
+{
+	struct ssh_rtl *rtl = ssh_request_rtl(rqst);
+	struct ssam_request_sync *r;
+
+	r = container_of(rqst, struct ssam_request_sync, base);
+	r->status = status;
+
+	if (r->resp)
+		r->resp->length = 0;
+
+	if (status) {
+		rtl_dbg_cond(rtl, "rsp: request failed: %d\n", status);
+		return;
+	}
+
+	if (!data)	/* Handle requests without a response. */
+		return;
+
+	if (!r->resp || !r->resp->pointer) {
+		if (data->len)
+			rtl_warn(rtl, "rsp: no response buffer provided, dropping data\n");
+		return;
+	}
+
+	if (data->len > r->resp->capacity) {
+		rtl_err(rtl,
+			"rsp: response buffer too small, capacity: %zu bytes, got: %zu bytes\n",
+			r->resp->capacity, data->len);
+		r->status = -ENOSPC;
+		return;
+	}
+
+	r->resp->length = data->len;
+	memcpy(r->resp->pointer, data->ptr, data->len);
+}
+
+static void ssam_request_sync_release(struct ssh_request *rqst)
+{
+	complete_all(&container_of(rqst, struct ssam_request_sync, base)->comp);
+}
+
+static const struct ssh_request_ops ssam_request_sync_ops = {
+	.release = ssam_request_sync_release,
+	.complete = ssam_request_sync_complete,
+};
+
+/**
+ * ssam_request_sync_alloc() - Allocate a synchronous request.
+ * @payload_len: The length of the request payload.
+ * @flags:       Flags used for allocation.
+ * @rqst:        Where to store the pointer to the allocated request.
+ * @buffer:      Where to store the buffer descriptor for the message buffer of
+ *               the request.
+ *
+ * Allocates a synchronous request with corresponding message buffer. The
+ * request still needs to be initialized ssam_request_sync_init() before
+ * it can be submitted, and the message buffer data must still be set to the
+ * returned buffer via ssam_request_sync_set_data() after it has been filled,
+ * if need be with adjusted message length.
+ *
+ * After use, the request and its corresponding message buffer should be freed
+ * via ssam_request_sync_free(). The buffer must not be freed separately.
+ *
+ * Return: Returns zero on success, %-ENOMEM if the request could not be
+ * allocated.
+ */
+int ssam_request_sync_alloc(size_t payload_len, gfp_t flags,
+			    struct ssam_request_sync **rqst,
+			    struct ssam_span *buffer)
+{
+	size_t msglen = SSH_COMMAND_MESSAGE_LENGTH(payload_len);
+
+	*rqst = kzalloc(sizeof(**rqst) + msglen, flags);
+	if (!*rqst)
+		return -ENOMEM;
+
+	buffer->ptr = (u8 *)(*rqst + 1);
+	buffer->len = msglen;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ssam_request_sync_alloc);
+
+/**
+ * ssam_request_sync_free() - Free a synchronous request.
+ * @rqst: The request to be freed.
+ *
+ * Free a synchronous request and its corresponding buffer allocated with
+ * ssam_request_sync_alloc(). Do not use for requests allocated on the stack
+ * or via any other function.
+ *
+ * Warning: The caller must ensure that the request is not in use any more.
+ * I.e. the caller must ensure that it has the only reference to the request
+ * and the request is not currently pending. This means that the caller has
+ * either never submitted the request, request submission has failed, or the
+ * caller has waited until the submitted request has been completed via
+ * ssam_request_sync_wait().
+ */
+void ssam_request_sync_free(struct ssam_request_sync *rqst)
+{
+	kfree(rqst);
+}
+EXPORT_SYMBOL_GPL(ssam_request_sync_free);
+
+/**
+ * ssam_request_sync_init() - Initialize a synchronous request struct.
+ * @rqst:  The request to initialize.
+ * @flags: The request flags.
+ *
+ * Initializes the given request struct. Does not initialize the request
+ * message data. This has to be done explicitly after this call via
+ * ssam_request_sync_set_data() and the actual message data has to be written
+ * via ssam_request_write_data().
+ *
+ * Return: Returns zero on success or %-EINVAL if the given flags are invalid.
+ */
+int ssam_request_sync_init(struct ssam_request_sync *rqst,
+			   enum ssam_request_flags flags)
+{
+	int status;
+
+	status = ssh_request_init(&rqst->base, flags, &ssam_request_sync_ops);
+	if (status)
+		return status;
+
+	init_completion(&rqst->comp);
+	rqst->resp = NULL;
+	rqst->status = 0;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ssam_request_sync_init);
+
+/**
+ * ssam_request_sync_submit() - Submit a synchronous request.
+ * @ctrl: The controller with which to submit the request.
+ * @rqst: The request to submit.
+ *
+ * Submit a synchronous request. The request has to be initialized and
+ * properly set up, including response buffer (may be %NULL if no response is
+ * expected) and command message data. This function does not wait for the
+ * request to be completed.
+ *
+ * If this function succeeds, ssam_request_sync_wait() must be used to ensure
+ * that the request has been completed before the response data can be
+ * accessed and/or the request can be freed. On failure, the request may
+ * immediately be freed.
+ *
+ * This function may only be used if the controller is active, i.e. has been
+ * initialized and not suspended.
+ */
+int ssam_request_sync_submit(struct ssam_controller *ctrl,
+			     struct ssam_request_sync *rqst)
+{
+	int status;
+
+	/*
+	 * This is only a superficial check. In general, the caller needs to
+	 * ensure that the controller is initialized and is not (and does not
+	 * get) suspended during use, i.e. until the request has been completed
+	 * (if _absolutely_ necessary, by use of ssam_controller_statelock/
+	 * ssam_controller_stateunlock, but something like ssam_client_link
+	 * should be preferred as this needs to last until the request has been
+	 * completed).
+	 *
+	 * Note that it is actually safe to use this function while the
+	 * controller is in the process of being shut down (as ssh_rtl_submit
+	 * is safe with regards to this), but it is generally discouraged to do
+	 * so.
+	 */
+	if (WARN_ON(READ_ONCE(ctrl->state) != SSAM_CONTROLLER_STARTED)) {
+		ssh_request_put(&rqst->base);
+		return -ENODEV;
+	}
+
+	status = ssh_rtl_submit(&ctrl->rtl, &rqst->base);
+	ssh_request_put(&rqst->base);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(ssam_request_sync_submit);
+
+/**
+ * ssam_request_sync() - Execute a synchronous request.
+ * @ctrl: The controller via which the request will be submitted.
+ * @spec: The request specification and payload.
+ * @rsp:  The response buffer.
+ *
+ * Allocates a synchronous request with its message data buffer on the heap
+ * via ssam_request_sync_alloc(), fully initializes it via the provided
+ * request specification, submits it, and finally waits for its completion
+ * before freeing it and returning its status.
+ *
+ * Return: Returns the status of the request or any failure during setup.
+ */
+int ssam_request_sync(struct ssam_controller *ctrl,
+		      const struct ssam_request *spec,
+		      struct ssam_response *rsp)
+{
+	struct ssam_request_sync *rqst;
+	struct ssam_span buf;
+	ssize_t len;
+	int status;
+
+	status = ssam_request_sync_alloc(spec->length, GFP_KERNEL, &rqst, &buf);
+	if (status)
+		return status;
+
+	status = ssam_request_sync_init(rqst, spec->flags);
+	if (status) {
+		ssam_request_sync_free(rqst);
+		return status;
+	}
+
+	ssam_request_sync_set_resp(rqst, rsp);
+
+	len = ssam_request_write_data(&buf, ctrl, spec);
+	if (len < 0) {
+		ssam_request_sync_free(rqst);
+		return len;
+	}
+
+	ssam_request_sync_set_data(rqst, buf.ptr, len);
+
+	status = ssam_request_sync_submit(ctrl, rqst);
+	if (!status)
+		status = ssam_request_sync_wait(rqst);
+
+	ssam_request_sync_free(rqst);
+	return status;
+}
+EXPORT_SYMBOL_GPL(ssam_request_sync);
+
+/**
+ * ssam_request_sync_with_buffer() - Execute a synchronous request with the
+ * provided buffer as back-end for the message buffer.
+ * @ctrl: The controller via which the request will be submitted.
+ * @spec: The request specification and payload.
+ * @rsp:  The response buffer.
+ * @buf:  The buffer for the request message data.
+ *
+ * Allocates a synchronous request struct on the stack, fully initializes it
+ * using the provided buffer as message data buffer, submits it, and then
+ * waits for its completion before returning its status. The
+ * SSH_COMMAND_MESSAGE_LENGTH() macro can be used to compute the required
+ * message buffer size.
+ *
+ * This function does essentially the same as ssam_request_sync(), but instead
+ * of dynamically allocating the request and message data buffer, it uses the
+ * provided message data buffer and stores the (small) request struct on the
+ * heap.
+ *
+ * Return: Returns the status of the request or any failure during setup.
+ */
+int ssam_request_sync_with_buffer(struct ssam_controller *ctrl,
+				  const struct ssam_request *spec,
+				  struct ssam_response *rsp,
+				  struct ssam_span *buf)
+{
+	struct ssam_request_sync rqst;
+	ssize_t len;
+	int status;
+
+	status = ssam_request_sync_init(&rqst, spec->flags);
+	if (status)
+		return status;
+
+	ssam_request_sync_set_resp(&rqst, rsp);
+
+	len = ssam_request_write_data(buf, ctrl, spec);
+	if (len < 0)
+		return len;
+
+	ssam_request_sync_set_data(&rqst, buf->ptr, len);
+
+	status = ssam_request_sync_submit(ctrl, &rqst);
+	if (!status)
+		status = ssam_request_sync_wait(&rqst);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(ssam_request_sync_with_buffer);
+
+
+/* -- Internal SAM requests. ------------------------------------------------ */
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_get_firmware_version, __le32, {
+	.target_category = SSAM_SSH_TC_SAM,
+	.target_id       = 0x01,
+	.command_id      = 0x13,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_off, u8, {
+	.target_category = SSAM_SSH_TC_SAM,
+	.target_id       = 0x01,
+	.command_id      = 0x15,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_on, u8, {
+	.target_category = SSAM_SSH_TC_SAM,
+	.target_id       = 0x01,
+	.command_id      = 0x16,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_exit, u8, {
+	.target_category = SSAM_SSH_TC_SAM,
+	.target_id       = 0x01,
+	.command_id      = 0x33,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_entry, u8, {
+	.target_category = SSAM_SSH_TC_SAM,
+	.target_id       = 0x01,
+	.command_id      = 0x34,
+	.instance_id     = 0x00,
+});
+
+/**
+ * struct ssh_notification_params - Command payload to enable/disable SSH
+ * notifications.
+ * @target_category: The target category for which notifications should be
+ *                   enabled/disabled.
+ * @flags:           Flags determining how notifications are being sent.
+ * @request_id:      The request ID that is used to send these notifications.
+ * @instance_id:     The specific instance in the given target category for
+ *                   which notifications should be enabled.
+ */
+struct ssh_notification_params {
+	u8 target_category;
+	u8 flags;
+	__le16 request_id;
+	u8 instance_id;
+} __packed;
+
+static_assert(sizeof(struct ssh_notification_params) == 5);
+
+static int __ssam_ssh_event_request(struct ssam_controller *ctrl,
+				    struct ssam_event_registry reg, u8 cid,
+				    struct ssam_event_id id, u8 flags)
+{
+	struct ssh_notification_params params;
+	struct ssam_request rqst;
+	struct ssam_response result;
+	int status;
+
+	u16 rqid = ssh_tc_to_rqid(id.target_category);
+	u8 buf = 0;
+
+	/* Only allow RQIDs that lie within the event spectrum. */
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	params.target_category = id.target_category;
+	params.instance_id = id.instance;
+	params.flags = flags;
+	put_unaligned_le16(rqid, &params.request_id);
+
+	rqst.target_category = reg.target_category;
+	rqst.target_id = reg.target_id;
+	rqst.command_id = cid;
+	rqst.instance_id = 0x00;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(params);
+	rqst.payload = (u8 *)&params;
+
+	result.capacity = sizeof(buf);
+	result.length = 0;
+	result.pointer = &buf;
+
+	status = ssam_retry(ssam_request_sync_onstack, ctrl, &rqst, &result,
+			    sizeof(params));
+
+	return status < 0 ? status : buf;
+}
+
+/**
+ * ssam_ssh_event_enable() - Enable SSH event.
+ * @ctrl:  The controller for which to enable the event.
+ * @reg:   The event registry describing what request to use for enabling and
+ *         disabling the event.
+ * @id:    The event identifier.
+ * @flags: The event flags.
+ *
+ * Enables the specified event on the EC. This function does not manage
+ * reference counting of enabled events and is basically only a wrapper for
+ * the raw EC request. If the specified event is already enabled, the EC will
+ * ignore this request.
+ *
+ * Return: Returns the status of the executed SAM request (zero on success and
+ * negative on direct failure) or %-EPROTO if the request response indicates a
+ * failure.
+ */
+static int ssam_ssh_event_enable(struct ssam_controller *ctrl,
+				 struct ssam_event_registry reg,
+				 struct ssam_event_id id, u8 flags)
+{
+	int status;
+
+	status = __ssam_ssh_event_request(ctrl, reg, reg.cid_enable, id, flags);
+
+	if (status < 0 && status != -EINVAL) {
+		ssam_err(ctrl,
+			 "failed to enable event source (tc: %#04x, iid: %#04x, reg: %#04x)\n",
+			 id.target_category, id.instance, reg.target_category);
+	}
+
+	if (status > 0) {
+		ssam_err(ctrl,
+			 "unexpected result while enabling event source: %#04x (tc: %#04x, iid: %#04x, reg: %#04x)\n",
+			 status, id.target_category, id.instance, reg.target_category);
+		return -EPROTO;
+	}
+
+	return status;
+}
+
+/**
+ * ssam_ssh_event_disable() - Disable SSH event.
+ * @ctrl:  The controller for which to disable the event.
+ * @reg:   The event registry describing what request to use for enabling and
+ *         disabling the event (must be same as used when enabling the event).
+ * @id:    The event identifier.
+ * @flags: The event flags (likely ignored for disabling of events).
+ *
+ * Disables the specified event on the EC. This function does not manage
+ * reference counting of enabled events and is basically only a wrapper for
+ * the raw EC request. If the specified event is already disabled, the EC will
+ * ignore this request.
+ *
+ * Return: Returns the status of the executed SAM request (zero on success and
+ * negative on direct failure) or %-EPROTO if the request response indicates a
+ * failure.
+ */
+static int ssam_ssh_event_disable(struct ssam_controller *ctrl,
+				  struct ssam_event_registry reg,
+				  struct ssam_event_id id, u8 flags)
+{
+	int status;
+
+	status = __ssam_ssh_event_request(ctrl, reg, reg.cid_disable, id, flags);
+
+	if (status < 0 && status != -EINVAL) {
+		ssam_err(ctrl,
+			 "failed to disable event source (tc: %#04x, iid: %#04x, reg: %#04x)\n",
+			 id.target_category, id.instance, reg.target_category);
+	}
+
+	if (status > 0) {
+		ssam_err(ctrl,
+			 "unexpected result while disabling event source: %#04x (tc: %#04x, iid: %#04x, reg: %#04x)\n",
+			 status, id.target_category, id.instance, reg.target_category);
+		return -EPROTO;
+	}
+
+	return status;
+}
+
+
+/* -- Wrappers for internal SAM requests. ----------------------------------- */
+
+/**
+ * ssam_get_firmware_version() - Get the SAM/EC firmware version.
+ * @ctrl:    The controller.
+ * @version: Where to store the version number.
+ *
+ * Return: Returns zero on success or the status of the executed SAM request
+ * if that request failed.
+ */
+int ssam_get_firmware_version(struct ssam_controller *ctrl, u32 *version)
+{
+	__le32 __version;
+	int status;
+
+	status = ssam_retry(ssam_ssh_get_firmware_version, ctrl, &__version);
+	if (status)
+		return status;
+
+	*version = le32_to_cpu(__version);
+	return 0;
+}
+
+/**
+ * ssam_ctrl_notif_display_off() - Notify EC that the display has been turned
+ * off.
+ * @ctrl: The controller.
+ *
+ * Notify the EC that the display has been turned off and the driver may enter
+ * a lower-power state. This will prevent events from being sent directly.
+ * Rather, the EC signals an event by pulling the wakeup GPIO high for as long
+ * as there are pending events. The events then need to be manually released,
+ * one by one, via the GPIO callback request. All pending events accumulated
+ * during this state can also be released by issuing the display-on
+ * notification, e.g. via ssam_ctrl_notif_display_on(), which will also reset
+ * the GPIO.
+ *
+ * On some devices, specifically ones with an integrated keyboard, the keyboard
+ * backlight will be turned off by this call.
+ *
+ * This function will only send the display-off notification command if
+ * display notifications are supported by the EC. Currently all known devices
+ * support these notifications.
+ *
+ * Use ssam_ctrl_notif_display_on() to reverse the effects of this function.
+ *
+ * Return: Returns zero on success or if no request has been executed, the
+ * status of the executed SAM request if that request failed, or %-EPROTO if
+ * an unexpected response has been received.
+ */
+int ssam_ctrl_notif_display_off(struct ssam_controller *ctrl)
+{
+	int status;
+	u8 response;
+
+	ssam_dbg(ctrl, "pm: notifying display off\n");
+
+	status = ssam_retry(ssam_ssh_notif_display_off, ctrl, &response);
+	if (status)
+		return status;
+
+	if (response != 0) {
+		ssam_err(ctrl, "unexpected response from display-off notification: %#04x\n",
+			 response);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+/**
+ * ssam_ctrl_notif_display_on() - Notify EC that the display has been turned on.
+ * @ctrl: The controller.
+ *
+ * Notify the EC that the display has been turned back on and the driver has
+ * exited its lower-power state. This notification is the counterpart to the
+ * display-off notification sent via ssam_ctrl_notif_display_off() and will
+ * reverse its effects, including resetting events to their default behavior.
+ *
+ * This function will only send the display-on notification command if display
+ * notifications are supported by the EC. Currently all known devices support
+ * these notifications.
+ *
+ * See ssam_ctrl_notif_display_off() for more details.
+ *
+ * Return: Returns zero on success or if no request has been executed, the
+ * status of the executed SAM request if that request failed, or %-EPROTO if
+ * an unexpected response has been received.
+ */
+int ssam_ctrl_notif_display_on(struct ssam_controller *ctrl)
+{
+	int status;
+	u8 response;
+
+	ssam_dbg(ctrl, "pm: notifying display on\n");
+
+	status = ssam_retry(ssam_ssh_notif_display_on, ctrl, &response);
+	if (status)
+		return status;
+
+	if (response != 0) {
+		ssam_err(ctrl, "unexpected response from display-on notification: %#04x\n",
+			 response);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+/**
+ * ssam_ctrl_notif_d0_exit() - Notify EC that the driver/device exits the D0
+ * power state.
+ * @ctrl: The controller
+ *
+ * Notifies the EC that the driver prepares to exit the D0 power state in
+ * favor of a lower-power state. Exact effects of this function related to the
+ * EC are currently unknown.
+ *
+ * This function will only send the D0-exit notification command if D0-state
+ * notifications are supported by the EC. Only newer Surface generations
+ * support these notifications.
+ *
+ * Use ssam_ctrl_notif_d0_entry() to reverse the effects of this function.
+ *
+ * Return: Returns zero on success or if no request has been executed, the
+ * status of the executed SAM request if that request failed, or %-EPROTO if
+ * an unexpected response has been received.
+ */
+int ssam_ctrl_notif_d0_exit(struct ssam_controller *ctrl)
+{
+	int status;
+	u8 response;
+
+	if (!ctrl->caps.d3_closes_handle)
+		return 0;
+
+	ssam_dbg(ctrl, "pm: notifying D0 exit\n");
+
+	status = ssam_retry(ssam_ssh_notif_d0_exit, ctrl, &response);
+	if (status)
+		return status;
+
+	if (response != 0) {
+		ssam_err(ctrl, "unexpected response from D0-exit notification: %#04x\n",
+			 response);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+/**
+ * ssam_ctrl_notif_d0_entry() - Notify EC that the driver/device enters the D0
+ * power state.
+ * @ctrl: The controller
+ *
+ * Notifies the EC that the driver has exited a lower-power state and entered
+ * the D0 power state. Exact effects of this function related to the EC are
+ * currently unknown.
+ *
+ * This function will only send the D0-entry notification command if D0-state
+ * notifications are supported by the EC. Only newer Surface generations
+ * support these notifications.
+ *
+ * See ssam_ctrl_notif_d0_exit() for more details.
+ *
+ * Return: Returns zero on success or if no request has been executed, the
+ * status of the executed SAM request if that request failed, or %-EPROTO if
+ * an unexpected response has been received.
+ */
+int ssam_ctrl_notif_d0_entry(struct ssam_controller *ctrl)
+{
+	int status;
+	u8 response;
+
+	if (!ctrl->caps.d3_closes_handle)
+		return 0;
+
+	ssam_dbg(ctrl, "pm: notifying D0 entry\n");
+
+	status = ssam_retry(ssam_ssh_notif_d0_entry, ctrl, &response);
+	if (status)
+		return status;
+
+	if (response != 0) {
+		ssam_err(ctrl, "unexpected response from D0-entry notification: %#04x\n",
+			 response);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+
+/* -- Top-level event registry interface. ----------------------------------- */
+
+/**
+ * ssam_nf_refcount_enable() - Enable event for reference count entry if it has
+ * not already been enabled.
+ * @ctrl:  The controller to enable the event on.
+ * @entry: The reference count entry for the event to be enabled.
+ * @flags: The flags used for enabling the event on the EC.
+ *
+ * Enable the event associated with the given reference count entry if the
+ * reference count equals one, i.e. the event has not previously been enabled.
+ * If the event has already been enabled (i.e. reference count not equal to
+ * one), check that the flags used for enabling match and warn about this if
+ * they do not.
+ *
+ * This does not modify the reference count itself, which is done with
+ * ssam_nf_refcount_inc() / ssam_nf_refcount_dec().
+ *
+ * Note: ``nf->lock`` must be held when calling this function.
+ *
+ * Return: Returns zero on success. If the event is enabled by this call,
+ * returns the status of the event-enable EC command.
+ */
+static int ssam_nf_refcount_enable(struct ssam_controller *ctrl,
+				   struct ssam_nf_refcount_entry *entry, u8 flags)
+{
+	const struct ssam_event_registry reg = entry->key.reg;
+	const struct ssam_event_id id = entry->key.id;
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	int status;
+
+	lockdep_assert_held(&nf->lock);
+
+	ssam_dbg(ctrl, "enabling event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
+		 reg.target_category, id.target_category, id.instance, entry->refcount);
+
+	if (entry->refcount == 1) {
+		status = ssam_ssh_event_enable(ctrl, reg, id, flags);
+		if (status)
+			return status;
+
+		entry->flags = flags;
+
+	} else if (entry->flags != flags) {
+		ssam_warn(ctrl,
+			  "inconsistent flags when enabling event: got %#04x, expected %#04x (reg: %#04x, tc: %#04x, iid: %#04x)\n",
+			  flags, entry->flags, reg.target_category, id.target_category,
+			  id.instance);
+	}
+
+	return 0;
+}
+
+/**
+ * ssam_nf_refcount_disable_free() - Disable event for reference count entry if
+ * it is no longer in use and free the corresponding entry.
+ * @ctrl:  The controller to disable the event on.
+ * @entry: The reference count entry for the event to be disabled.
+ * @flags: The flags used for enabling the event on the EC.
+ * @ec:    Flag specifying if the event should actually be disabled on the EC.
+ *
+ * If ``ec`` equals ``true`` and the reference count equals zero (i.e. the
+ * event is no longer requested by any client), the specified event will be
+ * disabled on the EC via the corresponding request.
+ *
+ * If ``ec`` equals ``false``, no request will be sent to the EC and the event
+ * can be considered in a detached state (i.e. no longer used but still
+ * enabled). Disabling an event via this method may be required for
+ * hot-removable devices, where event disable requests may time out after the
+ * device has been physically removed.
+ *
+ * In both cases, if the reference count equals zero, the corresponding
+ * reference count entry will be freed. The reference count entry must not be
+ * used any more after a call to this function.
+ *
+ * Also checks if the flags used for disabling the event match the flags used
+ * for enabling the event and warns if they do not (regardless of reference
+ * count).
+ *
+ * This does not modify the reference count itself, which is done with
+ * ssam_nf_refcount_inc() / ssam_nf_refcount_dec().
+ *
+ * Note: ``nf->lock`` must be held when calling this function.
+ *
+ * Return: Returns zero on success. If the event is disabled by this call,
+ * returns the status of the event-enable EC command.
+ */
+static int ssam_nf_refcount_disable_free(struct ssam_controller *ctrl,
+					 struct ssam_nf_refcount_entry *entry, u8 flags, bool ec)
+{
+	const struct ssam_event_registry reg = entry->key.reg;
+	const struct ssam_event_id id = entry->key.id;
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	int status = 0;
+
+	lockdep_assert_held(&nf->lock);
+
+	ssam_dbg(ctrl, "%s event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
+		 ec ? "disabling" : "detaching", reg.target_category, id.target_category,
+		 id.instance, entry->refcount);
+
+	if (entry->flags != flags) {
+		ssam_warn(ctrl,
+			  "inconsistent flags when disabling event: got %#04x, expected %#04x (reg: %#04x, tc: %#04x, iid: %#04x)\n",
+			  flags, entry->flags, reg.target_category, id.target_category,
+			  id.instance);
+	}
+
+	if (ec && entry->refcount == 0) {
+		status = ssam_ssh_event_disable(ctrl, reg, id, flags);
+		kfree(entry);
+	}
+
+	return status;
+}
+
+/**
+ * ssam_notifier_register() - Register an event notifier.
+ * @ctrl: The controller to register the notifier on.
+ * @n:    The event notifier to register.
+ *
+ * Register an event notifier. Increment the usage counter of the associated
+ * SAM event if the notifier is not marked as an observer. If the event is not
+ * marked as an observer and is currently not enabled, it will be enabled
+ * during this call. If the notifier is marked as an observer, no attempt will
+ * be made at enabling any event and no reference count will be modified.
+ *
+ * Notifiers marked as observers do not need to be associated with one specific
+ * event, i.e. as long as no event matching is performed, only the event target
+ * category needs to be set.
+ *
+ * Return: Returns zero on success, %-ENOSPC if there have already been
+ * %INT_MAX notifiers for the event ID/type associated with the notifier block
+ * registered, %-ENOMEM if the corresponding event entry could not be
+ * allocated. If this is the first time that a notifier block is registered
+ * for the specific associated event, returns the status of the event-enable
+ * EC-command.
+ */
+int ssam_notifier_register(struct ssam_controller *ctrl, struct ssam_event_notifier *n)
+{
+	u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
+	struct ssam_nf_refcount_entry *entry = NULL;
+	struct ssam_nf_head *nf_head;
+	struct ssam_nf *nf;
+	int status;
+
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	nf = &ctrl->cplt.event.notif;
+	nf_head = &nf->head[ssh_rqid_to_event(rqid)];
+
+	mutex_lock(&nf->lock);
+
+	if (!(n->flags & SSAM_EVENT_NOTIFIER_OBSERVER)) {
+		entry = ssam_nf_refcount_inc(nf, n->event.reg, n->event.id);
+		if (IS_ERR(entry)) {
+			mutex_unlock(&nf->lock);
+			return PTR_ERR(entry);
+		}
+	}
+
+	status = ssam_nfblk_insert(nf_head, &n->base);
+	if (status) {
+		if (entry)
+			ssam_nf_refcount_dec_free(nf, n->event.reg, n->event.id);
+
+		mutex_unlock(&nf->lock);
+		return status;
+	}
+
+	if (entry) {
+		status = ssam_nf_refcount_enable(ctrl, entry, n->event.flags);
+		if (status) {
+			ssam_nfblk_remove(&n->base);
+			ssam_nf_refcount_dec_free(nf, n->event.reg, n->event.id);
+			mutex_unlock(&nf->lock);
+			synchronize_srcu(&nf_head->srcu);
+			return status;
+		}
+	}
+
+	mutex_unlock(&nf->lock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ssam_notifier_register);
+
+/**
+ * __ssam_notifier_unregister() - Unregister an event notifier.
+ * @ctrl:    The controller the notifier has been registered on.
+ * @n:       The event notifier to unregister.
+ * @disable: Whether to disable the corresponding event on the EC.
+ *
+ * Unregister an event notifier. Decrement the usage counter of the associated
+ * SAM event if the notifier is not marked as an observer. If the usage counter
+ * reaches zero and ``disable`` equals ``true``, the event will be disabled.
+ *
+ * Useful for hot-removable devices, where communication may fail once the
+ * device has been physically removed. In that case, specifying ``disable`` as
+ * ``false`` avoids communication with the EC.
+ *
+ * Return: Returns zero on success, %-ENOENT if the given notifier block has
+ * not been registered on the controller. If the given notifier block was the
+ * last one associated with its specific event, returns the status of the
+ * event-disable EC-command.
+ */
+int __ssam_notifier_unregister(struct ssam_controller *ctrl, struct ssam_event_notifier *n,
+			       bool disable)
+{
+	u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
+	struct ssam_nf_refcount_entry *entry;
+	struct ssam_nf_head *nf_head;
+	struct ssam_nf *nf;
+	int status = 0;
+
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	nf = &ctrl->cplt.event.notif;
+	nf_head = &nf->head[ssh_rqid_to_event(rqid)];
+
+	mutex_lock(&nf->lock);
+
+	if (!ssam_nfblk_find(nf_head, &n->base)) {
+		mutex_unlock(&nf->lock);
+		return -ENOENT;
+	}
+
+	/*
+	 * If this is an observer notifier, do not attempt to disable the
+	 * event, just remove it.
+	 */
+	if (!(n->flags & SSAM_EVENT_NOTIFIER_OBSERVER)) {
+		entry = ssam_nf_refcount_dec(nf, n->event.reg, n->event.id);
+		if (WARN_ON(!entry)) {
+			/*
+			 * If this does not return an entry, there's a logic
+			 * error somewhere: The notifier block is registered,
+			 * but the event refcount entry is not there. Remove
+			 * the notifier block anyways.
+			 */
+			status = -ENOENT;
+			goto remove;
+		}
+
+		status = ssam_nf_refcount_disable_free(ctrl, entry, n->event.flags, disable);
+	}
+
+remove:
+	ssam_nfblk_remove(&n->base);
+	mutex_unlock(&nf->lock);
+	synchronize_srcu(&nf_head->srcu);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(__ssam_notifier_unregister);
+
+/**
+ * ssam_controller_event_enable() - Enable the specified event.
+ * @ctrl:  The controller to enable the event for.
+ * @reg:   The event registry to use for enabling the event.
+ * @id:    The event ID specifying the event to be enabled.
+ * @flags: The SAM event flags used for enabling the event.
+ *
+ * Increment the event reference count of the specified event. If the event has
+ * not been enabled previously, it will be enabled by this call.
+ *
+ * Note: In general, ssam_notifier_register() with a non-observer notifier
+ * should be preferred for enabling/disabling events, as this will guarantee
+ * proper ordering and event forwarding in case of errors during event
+ * enabling/disabling.
+ *
+ * Return: Returns zero on success, %-ENOSPC if the reference count for the
+ * specified event has reached its maximum, %-ENOMEM if the corresponding event
+ * entry could not be allocated. If this is the first time that this event has
+ * been enabled (i.e. the reference count was incremented from zero to one by
+ * this call), returns the status of the event-enable EC-command.
+ */
+int ssam_controller_event_enable(struct ssam_controller *ctrl,
+				 struct ssam_event_registry reg,
+				 struct ssam_event_id id, u8 flags)
+{
+	u16 rqid = ssh_tc_to_rqid(id.target_category);
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	struct ssam_nf_refcount_entry *entry;
+	int status;
+
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	mutex_lock(&nf->lock);
+
+	entry = ssam_nf_refcount_inc(nf, reg, id);
+	if (IS_ERR(entry)) {
+		mutex_unlock(&nf->lock);
+		return PTR_ERR(entry);
+	}
+
+	status = ssam_nf_refcount_enable(ctrl, entry, flags);
+	if (status) {
+		ssam_nf_refcount_dec_free(nf, reg, id);
+		mutex_unlock(&nf->lock);
+		return status;
+	}
+
+	mutex_unlock(&nf->lock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ssam_controller_event_enable);
+
+/**
+ * ssam_controller_event_disable() - Disable the specified event.
+ * @ctrl:  The controller to disable the event for.
+ * @reg:   The event registry to use for disabling the event.
+ * @id:    The event ID specifying the event to be disabled.
+ * @flags: The flags used when enabling the event.
+ *
+ * Decrement the reference count of the specified event. If the reference count
+ * reaches zero, the event will be disabled.
+ *
+ * Note: In general, ssam_notifier_register()/ssam_notifier_unregister() with a
+ * non-observer notifier should be preferred for enabling/disabling events, as
+ * this will guarantee proper ordering and event forwarding in case of errors
+ * during event enabling/disabling.
+ *
+ * Return: Returns zero on success, %-ENOENT if the given event has not been
+ * enabled on the controller. If the reference count of the event reaches zero
+ * during this call, returns the status of the event-disable EC-command.
+ */
+int ssam_controller_event_disable(struct ssam_controller *ctrl,
+				  struct ssam_event_registry reg,
+				  struct ssam_event_id id, u8 flags)
+{
+	u16 rqid = ssh_tc_to_rqid(id.target_category);
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	struct ssam_nf_refcount_entry *entry;
+	int status;
+
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	mutex_lock(&nf->lock);
+
+	entry = ssam_nf_refcount_dec(nf, reg, id);
+	if (!entry) {
+		mutex_unlock(&nf->lock);
+		return -ENOENT;
+	}
+
+	status = ssam_nf_refcount_disable_free(ctrl, entry, flags, true);
+
+	mutex_unlock(&nf->lock);
+	return status;
+}
+EXPORT_SYMBOL_GPL(ssam_controller_event_disable);
+
+/**
+ * ssam_notifier_disable_registered() - Disable events for all registered
+ * notifiers.
+ * @ctrl: The controller for which to disable the notifiers/events.
+ *
+ * Disables events for all currently registered notifiers. In case of an error
+ * (EC command failing), all previously disabled events will be restored and
+ * the error code returned.
+ *
+ * This function is intended to disable all events prior to hibernation entry.
+ * See ssam_notifier_restore_registered() to restore/re-enable all events
+ * disabled with this function.
+ *
+ * Note that this function will not disable events for notifiers registered
+ * after calling this function. It should thus be made sure that no new
+ * notifiers are going to be added after this call and before the corresponding
+ * call to ssam_notifier_restore_registered().
+ *
+ * Return: Returns zero on success. In case of failure returns the error code
+ * returned by the failed EC command to disable an event.
+ */
+int ssam_notifier_disable_registered(struct ssam_controller *ctrl)
+{
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	struct rb_node *n;
+	int status;
+
+	mutex_lock(&nf->lock);
+	for (n = rb_first(&nf->refcount); n; n = rb_next(n)) {
+		struct ssam_nf_refcount_entry *e;
+
+		e = rb_entry(n, struct ssam_nf_refcount_entry, node);
+		status = ssam_ssh_event_disable(ctrl, e->key.reg,
+						e->key.id, e->flags);
+		if (status)
+			goto err;
+	}
+	mutex_unlock(&nf->lock);
+
+	return 0;
+
+err:
+	for (n = rb_prev(n); n; n = rb_prev(n)) {
+		struct ssam_nf_refcount_entry *e;
+
+		e = rb_entry(n, struct ssam_nf_refcount_entry, node);
+		ssam_ssh_event_enable(ctrl, e->key.reg, e->key.id, e->flags);
+	}
+	mutex_unlock(&nf->lock);
+
+	return status;
+}
+
+/**
+ * ssam_notifier_restore_registered() - Restore/re-enable events for all
+ * registered notifiers.
+ * @ctrl: The controller for which to restore the notifiers/events.
+ *
+ * Restores/re-enables all events for which notifiers have been registered on
+ * the given controller. In case of a failure, the error is logged and the
+ * function continues to try and enable the remaining events.
+ *
+ * This function is intended to restore/re-enable all registered events after
+ * hibernation. See ssam_notifier_disable_registered() for the counter part
+ * disabling the events and more details.
+ */
+void ssam_notifier_restore_registered(struct ssam_controller *ctrl)
+{
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	struct rb_node *n;
+
+	mutex_lock(&nf->lock);
+	for (n = rb_first(&nf->refcount); n; n = rb_next(n)) {
+		struct ssam_nf_refcount_entry *e;
+
+		e = rb_entry(n, struct ssam_nf_refcount_entry, node);
+
+		/* Ignore errors, will get logged in call. */
+		ssam_ssh_event_enable(ctrl, e->key.reg, e->key.id, e->flags);
+	}
+	mutex_unlock(&nf->lock);
+}
+
+/**
+ * ssam_notifier_is_empty() - Check if there are any registered notifiers.
+ * @ctrl: The controller to check on.
+ *
+ * Return: Returns %true if there are currently no notifiers registered on the
+ * controller, %false otherwise.
+ */
+static bool ssam_notifier_is_empty(struct ssam_controller *ctrl)
+{
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	bool result;
+
+	mutex_lock(&nf->lock);
+	result = ssam_nf_refcount_empty(nf);
+	mutex_unlock(&nf->lock);
+
+	return result;
+}
+
+/**
+ * ssam_notifier_unregister_all() - Unregister all currently registered
+ * notifiers.
+ * @ctrl: The controller to unregister the notifiers on.
+ *
+ * Unregisters all currently registered notifiers. This function is used to
+ * ensure that all notifiers will be unregistered and associated
+ * entries/resources freed when the controller is being shut down.
+ */
+static void ssam_notifier_unregister_all(struct ssam_controller *ctrl)
+{
+	struct ssam_nf *nf = &ctrl->cplt.event.notif;
+	struct ssam_nf_refcount_entry *e, *n;
+
+	mutex_lock(&nf->lock);
+	rbtree_postorder_for_each_entry_safe(e, n, &nf->refcount, node) {
+		/* Ignore errors, will get logged in call. */
+		ssam_ssh_event_disable(ctrl, e->key.reg, e->key.id, e->flags);
+		kfree(e);
+	}
+	nf->refcount = RB_ROOT;
+	mutex_unlock(&nf->lock);
+}
+
+
+/* -- Wakeup IRQ. ----------------------------------------------------------- */
+
+static irqreturn_t ssam_irq_handle(int irq, void *dev_id)
+{
+	struct ssam_controller *ctrl = dev_id;
+
+	ssam_dbg(ctrl, "pm: wake irq triggered\n");
+
+	/*
+	 * Note: Proper wakeup detection is currently unimplemented.
+	 *       When the EC is in display-off or any other non-D0 state, it
+	 *       does not send events/notifications to the host. Instead it
+	 *       signals that there are events available via the wakeup IRQ.
+	 *       This driver is responsible for calling back to the EC to
+	 *       release these events one-by-one.
+	 *
+	 *       This IRQ should not cause a full system resume by its own.
+	 *       Instead, events should be handled by their respective subsystem
+	 *       drivers, which in turn should signal whether a full system
+	 *       resume should be performed.
+	 *
+	 * TODO: Send GPIO callback command repeatedly to EC until callback
+	 *       returns 0x00. Return flag of callback is "has more events".
+	 *       Each time the command is sent, one event is "released". Once
+	 *       all events have been released (return = 0x00), the GPIO is
+	 *       re-armed. Detect wakeup events during this process, go back to
+	 *       sleep if no wakeup event has been received.
+	 */
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * ssam_irq_setup() - Set up SAM EC wakeup-GPIO interrupt.
+ * @ctrl: The controller for which the IRQ should be set up.
+ *
+ * Set up an IRQ for the wakeup-GPIO pin of the SAM EC. This IRQ can be used
+ * to wake the device from a low power state.
+ *
+ * Note that this IRQ can only be triggered while the EC is in the display-off
+ * state. In this state, events are not sent to the host in the usual way.
+ * Instead the wakeup-GPIO gets pulled to "high" as long as there are pending
+ * events and these events need to be released one-by-one via the GPIO
+ * callback request, either until there are no events left and the GPIO is
+ * reset, or all at once by transitioning the EC out of the display-off state,
+ * which will also clear the GPIO.
+ *
+ * Not all events, however, should trigger a full system wakeup. Instead the
+ * driver should, if necessary, inspect and forward each event to the
+ * corresponding subsystem, which in turn should decide if the system needs to
+ * be woken up. This logic has not been implemented yet, thus wakeup by this
+ * IRQ should be disabled by default to avoid spurious wake-ups, caused, for
+ * example, by the remaining battery percentage changing. Refer to comments in
+ * this function and comments in the corresponding IRQ handler for more
+ * details on how this should be implemented.
+ *
+ * See also ssam_ctrl_notif_display_off() and ssam_ctrl_notif_display_off()
+ * for functions to transition the EC into and out of the display-off state as
+ * well as more details on it.
+ *
+ * The IRQ is disabled by default and has to be enabled before it can wake up
+ * the device from suspend via ssam_irq_arm_for_wakeup(). On teardown, the IRQ
+ * should be freed via ssam_irq_free().
+ */
+int ssam_irq_setup(struct ssam_controller *ctrl)
+{
+	struct device *dev = ssam_controller_device(ctrl);
+	struct gpio_desc *gpiod;
+	int irq;
+	int status;
+
+	/*
+	 * The actual GPIO interrupt is declared in ACPI as TRIGGER_HIGH.
+	 * However, the GPIO line only gets reset by sending the GPIO callback
+	 * command to SAM (or alternatively the display-on notification). As
+	 * proper handling for this interrupt is not implemented yet, leaving
+	 * the IRQ at TRIGGER_HIGH would cause an IRQ storm (as the callback
+	 * never gets sent and thus the line never gets reset). To avoid this,
+	 * mark the IRQ as TRIGGER_RISING for now, only creating a single
+	 * interrupt, and let the SAM resume callback during the controller
+	 * resume process clear it.
+	 */
+	const int irqf = IRQF_ONESHOT | IRQF_TRIGGER_RISING | IRQF_NO_AUTOEN;
+
+	gpiod = gpiod_get(dev, "ssam_wakeup-int", GPIOD_ASIS);
+	if (IS_ERR(gpiod))
+		return PTR_ERR(gpiod);
+
+	irq = gpiod_to_irq(gpiod);
+	gpiod_put(gpiod);
+
+	if (irq < 0)
+		return irq;
+
+	status = request_threaded_irq(irq, NULL, ssam_irq_handle, irqf,
+				      "ssam_wakeup", ctrl);
+	if (status)
+		return status;
+
+	ctrl->irq.num = irq;
+	return 0;
+}
+
+/**
+ * ssam_irq_free() - Free SAM EC wakeup-GPIO interrupt.
+ * @ctrl: The controller for which the IRQ should be freed.
+ *
+ * Free the wakeup-GPIO IRQ previously set-up via ssam_irq_setup().
+ */
+void ssam_irq_free(struct ssam_controller *ctrl)
+{
+	free_irq(ctrl->irq.num, ctrl);
+	ctrl->irq.num = -1;
+}
+
+/**
+ * ssam_irq_arm_for_wakeup() - Arm the EC IRQ for wakeup, if enabled.
+ * @ctrl: The controller for which the IRQ should be armed.
+ *
+ * Sets up the IRQ so that it can be used to wake the device. Specifically,
+ * this function enables the irq and then, if the device is allowed to wake up
+ * the system, calls enable_irq_wake(). See ssam_irq_disarm_wakeup() for the
+ * corresponding function to disable the IRQ.
+ *
+ * This function is intended to arm the IRQ before entering S2idle suspend.
+ *
+ * Note: calls to ssam_irq_arm_for_wakeup() and ssam_irq_disarm_wakeup() must
+ * be balanced.
+ */
+int ssam_irq_arm_for_wakeup(struct ssam_controller *ctrl)
+{
+	struct device *dev = ssam_controller_device(ctrl);
+	int status;
+
+	enable_irq(ctrl->irq.num);
+	if (device_may_wakeup(dev)) {
+		status = enable_irq_wake(ctrl->irq.num);
+		if (status) {
+			ssam_err(ctrl, "failed to enable wake IRQ: %d\n", status);
+			disable_irq(ctrl->irq.num);
+			return status;
+		}
+
+		ctrl->irq.wakeup_enabled = true;
+	} else {
+		ctrl->irq.wakeup_enabled = false;
+	}
+
+	return 0;
+}
+
+/**
+ * ssam_irq_disarm_wakeup() - Disarm the wakeup IRQ.
+ * @ctrl: The controller for which the IRQ should be disarmed.
+ *
+ * Disarm the IRQ previously set up for wake via ssam_irq_arm_for_wakeup().
+ *
+ * This function is intended to disarm the IRQ after exiting S2idle suspend.
+ *
+ * Note: calls to ssam_irq_arm_for_wakeup() and ssam_irq_disarm_wakeup() must
+ * be balanced.
+ */
+void ssam_irq_disarm_wakeup(struct ssam_controller *ctrl)
+{
+	int status;
+
+	if (ctrl->irq.wakeup_enabled) {
+		status = disable_irq_wake(ctrl->irq.num);
+		if (status)
+			ssam_err(ctrl, "failed to disable wake IRQ: %d\n", status);
+
+		ctrl->irq.wakeup_enabled = false;
+	}
+	disable_irq(ctrl->irq.num);
+}