Adding upstream version 6.6.15.upstream/6.6.15

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

11 files changed, 2987 insertions, 0 deletions

diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig
new file mode 100644
index 0000000000..eda6b11d40
--- /dev/null
+++ b/drivers/hwtracing/stm/Kconfig
@@ -0,0 +1,82 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config STM
+	tristate "System Trace Module devices"
+	select CONFIGFS_FS
+	help
+	  A System Trace Module (STM) is a device exporting data in System
+	  Trace Protocol (STP) format as defined by MIPI STP standards.
+	  Examples of such devices are Intel(R) Trace Hub and Coresight STM.
+
+	  Say Y here to enable System Trace Module device support.
+
+if STM
+
+config STM_PROTO_BASIC
+	tristate "Basic STM framing protocol driver"
+	default CONFIG_STM
+	help
+	  This is a simple framing protocol for sending data over STM
+	  devices. This was the protocol that the STM framework used
+	  exclusively until the MIPI SyS-T support was added. Use this
+	  driver for compatibility with your existing STM setup.
+
+	  The receiving side only needs to be able to decode the MIPI
+	  STP protocol in order to extract the data.
+
+	  If you want to be able to use the basic protocol or want the
+	  backwards compatibility for your existing setup, say Y.
+
+config STM_PROTO_SYS_T
+	tristate "MIPI SyS-T STM framing protocol driver"
+	default CONFIG_STM
+	help
+	  This is an implementation of MIPI SyS-T protocol to be used
+	  over the STP transport. In addition to the data payload, it
+	  also carries additional metadata for time correlation, better
+	  means of trace source identification, etc.
+
+	  The receiving side must be able to decode this protocol in
+	  addition to the MIPI STP, in order to extract the data.
+
+	  If you don't know what this is, say N.
+
+config STM_DUMMY
+	tristate "Dummy STM driver"
+	help
+	  This is a simple dummy device that pretends to be an stm device
+	  and discards your data. Use for stm class testing.
+
+	  If you don't know what this is, say N.
+
+config STM_SOURCE_CONSOLE
+	tristate "Kernel console over STM devices"
+	help
+	  This is a kernel space trace source that sends kernel log
+	  messages to trace hosts over STM devices.
+
+	  If you want to send kernel console messages over STM devices,
+	  say Y.
+
+config STM_SOURCE_HEARTBEAT
+	tristate "Heartbeat over STM devices"
+	help
+	  This is a kernel space trace source that sends periodic
+	  heartbeat messages to trace hosts over STM devices. It is
+	  also useful for testing stm class drivers and the stm class
+	  framework itself.
+
+	  If you want to send heartbeat messages over STM devices,
+	  say Y.
+
+config STM_SOURCE_FTRACE
+	tristate "Copy the output from kernel Ftrace to STM engine"
+	depends on TRACING
+	help
+	  This option can be used to copy the output from kernel Ftrace
+	  to STM engine. Enabling this option will introduce a slight
+	  timing effect.
+
+	  If you want to send kernel Ftrace messages over STM devices,
+	  say Y.
+
+endif
diff --git a/drivers/hwtracing/stm/Makefile b/drivers/hwtracing/stm/Makefile
new file mode 100644
index 0000000000..1692fcd292
--- /dev/null
+++ b/drivers/hwtracing/stm/Makefile
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_STM)	+= stm_core.o
+
+stm_core-y		:= core.o policy.o
+
+obj-$(CONFIG_STM_PROTO_BASIC) += stm_p_basic.o
+obj-$(CONFIG_STM_PROTO_SYS_T) += stm_p_sys-t.o
+
+stm_p_basic-y		:= p_basic.o
+stm_p_sys-t-y		:= p_sys-t.o
+
+obj-$(CONFIG_STM_DUMMY)	+= dummy_stm.o
+
+obj-$(CONFIG_STM_SOURCE_CONSOLE)	+= stm_console.o
+obj-$(CONFIG_STM_SOURCE_HEARTBEAT)	+= stm_heartbeat.o
+obj-$(CONFIG_STM_SOURCE_FTRACE)		+= stm_ftrace.o
+
+stm_console-y		:= console.o
+stm_heartbeat-y		:= heartbeat.o
+stm_ftrace-y		:= ftrace.o
diff --git a/drivers/hwtracing/stm/console.c b/drivers/hwtracing/stm/console.c
new file mode 100644
index 0000000000..a00f65e217
--- /dev/null
+++ b/drivers/hwtracing/stm/console.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple kernel console driver for STM devices
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * STM console will send kernel messages over STM devices to a trace host.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/console.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+
+static int stm_console_link(struct stm_source_data *data);
+static void stm_console_unlink(struct stm_source_data *data);
+
+static struct stm_console {
+	struct stm_source_data	data;
+	struct console		console;
+} stm_console = {
+	.data	= {
+		.name		= "console",
+		.nr_chans	= 1,
+		.link		= stm_console_link,
+		.unlink		= stm_console_unlink,
+	},
+};
+
+static void
+stm_console_write(struct console *con, const char *buf, unsigned len)
+{
+	struct stm_console *sc = container_of(con, struct stm_console, console);
+
+	stm_source_write(&sc->data, 0, buf, len);
+}
+
+static int stm_console_link(struct stm_source_data *data)
+{
+	struct stm_console *sc = container_of(data, struct stm_console, data);
+
+	strcpy(sc->console.name, "stm_console");
+	sc->console.write = stm_console_write;
+	sc->console.flags = CON_ENABLED | CON_PRINTBUFFER;
+	register_console(&sc->console);
+
+	return 0;
+}
+
+static void stm_console_unlink(struct stm_source_data *data)
+{
+	struct stm_console *sc = container_of(data, struct stm_console, data);
+
+	unregister_console(&sc->console);
+}
+
+static int stm_console_init(void)
+{
+	return stm_source_register_device(NULL, &stm_console.data);
+}
+
+static void stm_console_exit(void)
+{
+	stm_source_unregister_device(&stm_console.data);
+}
+
+module_init(stm_console_init);
+module_exit(stm_console_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("stm_console driver");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
new file mode 100644
index 0000000000..534fbefc7f
--- /dev/null
+++ b/drivers/hwtracing/stm/core.c
@@ -0,0 +1,1363 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Trace Module (STM) infrastructure
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * STM class implements generic infrastructure for  System Trace Module devices
+ * as defined in MIPI STPv2 specification.
+ */
+
+#include <linux/pm_runtime.h>
+#include <linux/uaccess.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/compat.h>
+#include <linux/kdev_t.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include "stm.h"
+
+#include <uapi/linux/stm.h>
+
+static unsigned int stm_core_up;
+
+/*
+ * The SRCU here makes sure that STM device doesn't disappear from under a
+ * stm_source_write() caller, which may want to have as little overhead as
+ * possible.
+ */
+static struct srcu_struct stm_source_srcu;
+
+static ssize_t masters_show(struct device *dev,
+			    struct device_attribute *attr,
+			    char *buf)
+{
+	struct stm_device *stm = to_stm_device(dev);
+	int ret;
+
+	ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
+
+	return ret;
+}
+
+static DEVICE_ATTR_RO(masters);
+
+static ssize_t channels_show(struct device *dev,
+			     struct device_attribute *attr,
+			     char *buf)
+{
+	struct stm_device *stm = to_stm_device(dev);
+	int ret;
+
+	ret = sprintf(buf, "%u\n", stm->data->sw_nchannels);
+
+	return ret;
+}
+
+static DEVICE_ATTR_RO(channels);
+
+static ssize_t hw_override_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct stm_device *stm = to_stm_device(dev);
+	int ret;
+
+	ret = sprintf(buf, "%u\n", stm->data->hw_override);
+
+	return ret;
+}
+
+static DEVICE_ATTR_RO(hw_override);
+
+static struct attribute *stm_attrs[] = {
+	&dev_attr_masters.attr,
+	&dev_attr_channels.attr,
+	&dev_attr_hw_override.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(stm);
+
+static struct class stm_class = {
+	.name		= "stm",
+	.dev_groups	= stm_groups,
+};
+
+/**
+ * stm_find_device() - find stm device by name
+ * @buf:	character buffer containing the name
+ *
+ * This is called when either policy gets assigned to an stm device or an
+ * stm_source device gets linked to an stm device.
+ *
+ * This grabs device's reference (get_device()) and module reference, both
+ * of which the calling path needs to make sure to drop with stm_put_device().
+ *
+ * Return:	stm device pointer or null if lookup failed.
+ */
+struct stm_device *stm_find_device(const char *buf)
+{
+	struct stm_device *stm;
+	struct device *dev;
+
+	if (!stm_core_up)
+		return NULL;
+
+	dev = class_find_device_by_name(&stm_class, buf);
+	if (!dev)
+		return NULL;
+
+	stm = to_stm_device(dev);
+	if (!try_module_get(stm->owner)) {
+		/* matches class_find_device() above */
+		put_device(dev);
+		return NULL;
+	}
+
+	return stm;
+}
+
+/**
+ * stm_put_device() - drop references on the stm device
+ * @stm:	stm device, previously acquired by stm_find_device()
+ *
+ * This drops the module reference and device reference taken by
+ * stm_find_device() or stm_char_open().
+ */
+void stm_put_device(struct stm_device *stm)
+{
+	module_put(stm->owner);
+	put_device(&stm->dev);
+}
+
+/*
+ * Internally we only care about software-writable masters here, that is the
+ * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
+ * original master numbers to be visible externally, since they are the ones
+ * that will appear in the STP stream. Thus, the internal bookkeeping uses
+ * $master - stm_data->sw_start to reference master descriptors and such.
+ */
+
+#define __stm_master(_s, _m)				\
+	((_s)->masters[(_m) - (_s)->data->sw_start])
+
+static inline struct stp_master *
+stm_master(struct stm_device *stm, unsigned int idx)
+{
+	if (idx < stm->data->sw_start || idx > stm->data->sw_end)
+		return NULL;
+
+	return __stm_master(stm, idx);
+}
+
+static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
+{
+	struct stp_master *master;
+
+	master = kzalloc(struct_size(master, chan_map,
+				     BITS_TO_LONGS(stm->data->sw_nchannels)),
+			 GFP_ATOMIC);
+	if (!master)
+		return -ENOMEM;
+
+	master->nr_free = stm->data->sw_nchannels;
+	__stm_master(stm, idx) = master;
+
+	return 0;
+}
+
+static void stp_master_free(struct stm_device *stm, unsigned int idx)
+{
+	struct stp_master *master = stm_master(stm, idx);
+
+	if (!master)
+		return;
+
+	__stm_master(stm, idx) = NULL;
+	kfree(master);
+}
+
+static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
+{
+	struct stp_master *master = stm_master(stm, output->master);
+
+	lockdep_assert_held(&stm->mc_lock);
+	lockdep_assert_held(&output->lock);
+
+	if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
+		return;
+
+	bitmap_allocate_region(&master->chan_map[0], output->channel,
+			       ilog2(output->nr_chans));
+
+	master->nr_free -= output->nr_chans;
+}
+
+static void
+stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
+{
+	struct stp_master *master = stm_master(stm, output->master);
+
+	lockdep_assert_held(&stm->mc_lock);
+	lockdep_assert_held(&output->lock);
+
+	bitmap_release_region(&master->chan_map[0], output->channel,
+			      ilog2(output->nr_chans));
+
+	master->nr_free += output->nr_chans;
+	output->nr_chans = 0;
+}
+
+/*
+ * This is like bitmap_find_free_region(), except it can ignore @start bits
+ * at the beginning.
+ */
+static int find_free_channels(unsigned long *bitmap, unsigned int start,
+			      unsigned int end, unsigned int width)
+{
+	unsigned int pos;
+	int i;
+
+	for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
+		pos = find_next_zero_bit(bitmap, end + 1, pos);
+		if (pos + width > end + 1)
+			break;
+
+		if (pos & (width - 1))
+			continue;
+
+		for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
+			;
+		if (i == width)
+			return pos;
+
+		/* step over [pos..pos+i) to continue search */
+		pos += i;
+	}
+
+	return -1;
+}
+
+static int
+stm_find_master_chan(struct stm_device *stm, unsigned int width,
+		     unsigned int *mstart, unsigned int mend,
+		     unsigned int *cstart, unsigned int cend)
+{
+	struct stp_master *master;
+	unsigned int midx;
+	int pos, err;
+
+	for (midx = *mstart; midx <= mend; midx++) {
+		if (!stm_master(stm, midx)) {
+			err = stp_master_alloc(stm, midx);
+			if (err)
+				return err;
+		}
+
+		master = stm_master(stm, midx);
+
+		if (!master->nr_free)
+			continue;
+
+		pos = find_free_channels(master->chan_map, *cstart, cend,
+					 width);
+		if (pos < 0)
+			continue;
+
+		*mstart = midx;
+		*cstart = pos;
+		return 0;
+	}
+
+	return -ENOSPC;
+}
+
+static int stm_output_assign(struct stm_device *stm, unsigned int width,
+			     struct stp_policy_node *policy_node,
+			     struct stm_output *output)
+{
+	unsigned int midx, cidx, mend, cend;
+	int ret = -EINVAL;
+
+	if (width > stm->data->sw_nchannels)
+		return -EINVAL;
+
+	/* We no longer accept policy_node==NULL here */
+	if (WARN_ON_ONCE(!policy_node))
+		return -EINVAL;
+
+	/*
+	 * Also, the caller holds reference to policy_node, so it won't
+	 * disappear on us.
+	 */
+	stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);
+
+	spin_lock(&stm->mc_lock);
+	spin_lock(&output->lock);
+	/* output is already assigned -- shouldn't happen */
+	if (WARN_ON_ONCE(output->nr_chans))
+		goto unlock;
+
+	ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
+	if (ret < 0)
+		goto unlock;
+
+	output->master = midx;
+	output->channel = cidx;
+	output->nr_chans = width;
+	if (stm->pdrv->output_open) {
+		void *priv = stp_policy_node_priv(policy_node);
+
+		if (WARN_ON_ONCE(!priv))
+			goto unlock;
+
+		/* configfs subsys mutex is held by the caller */
+		ret = stm->pdrv->output_open(priv, output);
+		if (ret)
+			goto unlock;
+	}
+
+	stm_output_claim(stm, output);
+	dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
+
+	ret = 0;
+unlock:
+	if (ret)
+		output->nr_chans = 0;
+
+	spin_unlock(&output->lock);
+	spin_unlock(&stm->mc_lock);
+
+	return ret;
+}
+
+static void stm_output_free(struct stm_device *stm, struct stm_output *output)
+{
+	spin_lock(&stm->mc_lock);
+	spin_lock(&output->lock);
+	if (output->nr_chans)
+		stm_output_disclaim(stm, output);
+	if (stm->pdrv && stm->pdrv->output_close)
+		stm->pdrv->output_close(output);
+	spin_unlock(&output->lock);
+	spin_unlock(&stm->mc_lock);
+}
+
+static void stm_output_init(struct stm_output *output)
+{
+	spin_lock_init(&output->lock);
+}
+
+static int major_match(struct device *dev, const void *data)
+{
+	unsigned int major = *(unsigned int *)data;
+
+	return MAJOR(dev->devt) == major;
+}
+
+/*
+ * Framing protocol management
+ * Modules can implement STM protocol drivers and (un-)register them
+ * with the STM class framework.
+ */
+static struct list_head stm_pdrv_head;
+static struct mutex stm_pdrv_mutex;
+
+struct stm_pdrv_entry {
+	struct list_head			entry;
+	const struct stm_protocol_driver	*pdrv;
+	const struct config_item_type		*node_type;
+};
+
+static const struct stm_pdrv_entry *
+__stm_lookup_protocol(const char *name)
+{
+	struct stm_pdrv_entry *pe;
+
+	/*
+	 * If no name is given (NULL or ""), fall back to "p_basic".
+	 */
+	if (!name || !*name)
+		name = "p_basic";
+
+	list_for_each_entry(pe, &stm_pdrv_head, entry) {
+		if (!strcmp(name, pe->pdrv->name))
+			return pe;
+	}
+
+	return NULL;
+}
+
+int stm_register_protocol(const struct stm_protocol_driver *pdrv)
+{
+	struct stm_pdrv_entry *pe = NULL;
+	int ret = -ENOMEM;
+
+	mutex_lock(&stm_pdrv_mutex);
+
+	if (__stm_lookup_protocol(pdrv->name)) {
+		ret = -EEXIST;
+		goto unlock;
+	}
+
+	pe = kzalloc(sizeof(*pe), GFP_KERNEL);
+	if (!pe)
+		goto unlock;
+
+	if (pdrv->policy_attr) {
+		pe->node_type = get_policy_node_type(pdrv->policy_attr);
+		if (!pe->node_type)
+			goto unlock;
+	}
+
+	list_add_tail(&pe->entry, &stm_pdrv_head);
+	pe->pdrv = pdrv;
+
+	ret = 0;
+unlock:
+	mutex_unlock(&stm_pdrv_mutex);
+
+	if (ret)
+		kfree(pe);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(stm_register_protocol);
+
+void stm_unregister_protocol(const struct stm_protocol_driver *pdrv)
+{
+	struct stm_pdrv_entry *pe, *iter;
+
+	mutex_lock(&stm_pdrv_mutex);
+
+	list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) {
+		if (pe->pdrv == pdrv) {
+			list_del(&pe->entry);
+
+			if (pe->node_type) {
+				kfree(pe->node_type->ct_attrs);
+				kfree(pe->node_type);
+			}
+			kfree(pe);
+			break;
+		}
+	}
+
+	mutex_unlock(&stm_pdrv_mutex);
+}
+EXPORT_SYMBOL_GPL(stm_unregister_protocol);
+
+static bool stm_get_protocol(const struct stm_protocol_driver *pdrv)
+{
+	return try_module_get(pdrv->owner);
+}
+
+void stm_put_protocol(const struct stm_protocol_driver *pdrv)
+{
+	module_put(pdrv->owner);
+}
+
+int stm_lookup_protocol(const char *name,
+			const struct stm_protocol_driver **pdrv,
+			const struct config_item_type **node_type)
+{
+	const struct stm_pdrv_entry *pe;
+
+	mutex_lock(&stm_pdrv_mutex);
+
+	pe = __stm_lookup_protocol(name);
+	if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) {
+		*pdrv = pe->pdrv;
+		*node_type = pe->node_type;
+	}
+
+	mutex_unlock(&stm_pdrv_mutex);
+
+	return pe ? 0 : -ENOENT;
+}
+
+static int stm_char_open(struct inode *inode, struct file *file)
+{
+	struct stm_file *stmf;
+	struct device *dev;
+	unsigned int major = imajor(inode);
+	int err = -ENOMEM;
+
+	dev = class_find_device(&stm_class, NULL, &major, major_match);
+	if (!dev)
+		return -ENODEV;
+
+	stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
+	if (!stmf)
+		goto err_put_device;
+
+	err = -ENODEV;
+	stm_output_init(&stmf->output);
+	stmf->stm = to_stm_device(dev);
+
+	if (!try_module_get(stmf->stm->owner))
+		goto err_free;
+
+	file->private_data = stmf;
+
+	return nonseekable_open(inode, file);
+
+err_free:
+	kfree(stmf);
+err_put_device:
+	/* matches class_find_device() above */
+	put_device(dev);
+
+	return err;
+}
+
+static int stm_char_release(struct inode *inode, struct file *file)
+{
+	struct stm_file *stmf = file->private_data;
+	struct stm_device *stm = stmf->stm;
+
+	if (stm->data->unlink)
+		stm->data->unlink(stm->data, stmf->output.master,
+				  stmf->output.channel);
+
+	stm_output_free(stm, &stmf->output);
+
+	/*
+	 * matches the stm_char_open()'s
+	 * class_find_device() + try_module_get()
+	 */
+	stm_put_device(stm);
+	kfree(stmf);
+
+	return 0;
+}
+
+static int
+stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
+			char **ids, unsigned int width)
+{
+	struct stp_policy_node *pn;
+	int err, n;
+
+	/*
+	 * On success, stp_policy_node_lookup() will return holding the
+	 * configfs subsystem mutex, which is then released in
+	 * stp_policy_node_put(). This allows the pdrv->output_open() in
+	 * stm_output_assign() to serialize against the attribute accessors.
+	 */
+	for (n = 0, pn = NULL; ids[n] && !pn; n++)
+		pn = stp_policy_node_lookup(stm, ids[n]);
+
+	if (!pn)
+		return -EINVAL;
+
+	err = stm_output_assign(stm, width, pn, output);
+
+	stp_policy_node_put(pn);
+
+	return err;
+}
+
+/**
+ * stm_data_write() - send the given payload as data packets
+ * @data:	stm driver's data
+ * @m:		STP master
+ * @c:		STP channel
+ * @ts_first:	timestamp the first packet
+ * @buf:	data payload buffer
+ * @count:	data payload size
+ */
+ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m,
+			       unsigned int c, bool ts_first, const void *buf,
+			       size_t count)
+{
+	unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0;
+	ssize_t sz;
+	size_t pos;
+
+	for (pos = 0, sz = 0; pos < count; pos += sz) {
+		sz = min_t(unsigned int, count - pos, 8);
+		sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz,
+				  &((u8 *)buf)[pos]);
+		if (sz <= 0)
+			break;
+
+		if (ts_first) {
+			flags = 0;
+			ts_first = false;
+		}
+	}
+
+	return sz < 0 ? sz : pos;
+}
+EXPORT_SYMBOL_GPL(stm_data_write);
+
+static ssize_t notrace
+stm_write(struct stm_device *stm, struct stm_output *output,
+	  unsigned int chan, const char *buf, size_t count)
+{
+	int err;
+
+	/* stm->pdrv is serialized against policy_mutex */
+	if (!stm->pdrv)
+		return -ENODEV;
+
+	err = stm->pdrv->write(stm->data, output, chan, buf, count);
+	if (err < 0)
+		return err;
+
+	return err;
+}
+
+static ssize_t stm_char_write(struct file *file, const char __user *buf,
+			      size_t count, loff_t *ppos)
+{
+	struct stm_file *stmf = file->private_data;
+	struct stm_device *stm = stmf->stm;
+	char *kbuf;
+	int err;
+
+	if (count + 1 > PAGE_SIZE)
+		count = PAGE_SIZE - 1;
+
+	/*
+	 * If no m/c have been assigned to this writer up to this
+	 * point, try to use the task name and "default" policy entries.
+	 */
+	if (!stmf->output.nr_chans) {
+		char comm[sizeof(current->comm)];
+		char *ids[] = { comm, "default", NULL };
+
+		get_task_comm(comm, current);
+
+		err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
+		/*
+		 * EBUSY means that somebody else just assigned this
+		 * output, which is just fine for write()
+		 */
+		if (err)
+			return err;
+	}
+
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	err = copy_from_user(kbuf, buf, count);
+	if (err) {
+		kfree(kbuf);
+		return -EFAULT;
+	}
+
+	pm_runtime_get_sync(&stm->dev);
+
+	count = stm_write(stm, &stmf->output, 0, kbuf, count);
+
+	pm_runtime_mark_last_busy(&stm->dev);
+	pm_runtime_put_autosuspend(&stm->dev);
+	kfree(kbuf);
+
+	return count;
+}
+
+static void stm_mmap_open(struct vm_area_struct *vma)
+{
+	struct stm_file *stmf = vma->vm_file->private_data;
+	struct stm_device *stm = stmf->stm;
+
+	pm_runtime_get(&stm->dev);
+}
+
+static void stm_mmap_close(struct vm_area_struct *vma)
+{
+	struct stm_file *stmf = vma->vm_file->private_data;
+	struct stm_device *stm = stmf->stm;
+
+	pm_runtime_mark_last_busy(&stm->dev);
+	pm_runtime_put_autosuspend(&stm->dev);
+}
+
+static const struct vm_operations_struct stm_mmap_vmops = {
+	.open	= stm_mmap_open,
+	.close	= stm_mmap_close,
+};
+
+static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct stm_file *stmf = file->private_data;
+	struct stm_device *stm = stmf->stm;
+	unsigned long size, phys;
+
+	if (!stm->data->mmio_addr)
+		return -EOPNOTSUPP;
+
+	if (vma->vm_pgoff)
+		return -EINVAL;
+
+	size = vma->vm_end - vma->vm_start;
+
+	if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
+		return -EINVAL;
+
+	phys = stm->data->mmio_addr(stm->data, stmf->output.master,
+				    stmf->output.channel,
+				    stmf->output.nr_chans);
+
+	if (!phys)
+		return -EINVAL;
+
+	pm_runtime_get_sync(&stm->dev);
+
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vm_flags_set(vma, VM_IO | VM_DONTEXPAND | VM_DONTDUMP);
+	vma->vm_ops = &stm_mmap_vmops;
+	vm_iomap_memory(vma, phys, size);
+
+	return 0;
+}
+
+static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
+{
+	struct stm_device *stm = stmf->stm;
+	struct stp_policy_id *id;
+	char *ids[] = { NULL, NULL };
+	int ret = -EINVAL, wlimit = 1;
+	u32 size;
+
+	if (stmf->output.nr_chans)
+		return -EBUSY;
+
+	if (copy_from_user(&size, arg, sizeof(size)))
+		return -EFAULT;
+
+	if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
+		return -EINVAL;
+
+	/*
+	 * size + 1 to make sure the .id string at the bottom is terminated,
+	 * which is also why memdup_user() is not useful here
+	 */
+	id = kzalloc(size + 1, GFP_KERNEL);
+	if (!id)
+		return -ENOMEM;
+
+	if (copy_from_user(id, arg, size)) {
+		ret = -EFAULT;
+		goto err_free;
+	}
+
+	if (id->__reserved_0 || id->__reserved_1)
+		goto err_free;
+
+	if (stm->data->sw_mmiosz)
+		wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
+
+	if (id->width < 1 || id->width > wlimit)
+		goto err_free;
+
+	ids[0] = id->id;
+	ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
+				      id->width);
+	if (ret)
+		goto err_free;
+
+	if (stm->data->link)
+		ret = stm->data->link(stm->data, stmf->output.master,
+				      stmf->output.channel);
+
+	if (ret)
+		stm_output_free(stmf->stm, &stmf->output);
+
+err_free:
+	kfree(id);
+
+	return ret;
+}
+
+static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
+{
+	struct stp_policy_id id = {
+		.size		= sizeof(id),
+		.master		= stmf->output.master,
+		.channel	= stmf->output.channel,
+		.width		= stmf->output.nr_chans,
+		.__reserved_0	= 0,
+		.__reserved_1	= 0,
+	};
+
+	return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
+}
+
+static long
+stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct stm_file *stmf = file->private_data;
+	struct stm_data *stm_data = stmf->stm->data;
+	int err = -ENOTTY;
+	u64 options;
+
+	switch (cmd) {
+	case STP_POLICY_ID_SET:
+		err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
+		if (err)
+			return err;
+
+		return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
+
+	case STP_POLICY_ID_GET:
+		return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
+
+	case STP_SET_OPTIONS:
+		if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
+			return -EFAULT;
+
+		if (stm_data->set_options)
+			err = stm_data->set_options(stm_data,
+						    stmf->output.master,
+						    stmf->output.channel,
+						    stmf->output.nr_chans,
+						    options);
+
+		break;
+	default:
+		break;
+	}
+
+	return err;
+}
+
+static const struct file_operations stm_fops = {
+	.open		= stm_char_open,
+	.release	= stm_char_release,
+	.write		= stm_char_write,
+	.mmap		= stm_char_mmap,
+	.unlocked_ioctl	= stm_char_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.llseek		= no_llseek,
+};
+
+static void stm_device_release(struct device *dev)
+{
+	struct stm_device *stm = to_stm_device(dev);
+
+	vfree(stm);
+}
+
+int stm_register_device(struct device *parent, struct stm_data *stm_data,
+			struct module *owner)
+{
+	struct stm_device *stm;
+	unsigned int nmasters;
+	int err = -ENOMEM;
+
+	if (!stm_core_up)
+		return -EPROBE_DEFER;
+
+	if (!stm_data->packet || !stm_data->sw_nchannels)
+		return -EINVAL;
+
+	nmasters = stm_data->sw_end - stm_data->sw_start + 1;
+	stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *));
+	if (!stm)
+		return -ENOMEM;
+
+	stm->major = register_chrdev(0, stm_data->name, &stm_fops);
+	if (stm->major < 0)
+		goto err_free;
+
+	device_initialize(&stm->dev);
+	stm->dev.devt = MKDEV(stm->major, 0);
+	stm->dev.class = &stm_class;
+	stm->dev.parent = parent;
+	stm->dev.release = stm_device_release;
+
+	mutex_init(&stm->link_mutex);
+	spin_lock_init(&stm->link_lock);
+	INIT_LIST_HEAD(&stm->link_list);
+
+	/* initialize the object before it is accessible via sysfs */
+	spin_lock_init(&stm->mc_lock);
+	mutex_init(&stm->policy_mutex);
+	stm->sw_nmasters = nmasters;
+	stm->owner = owner;
+	stm->data = stm_data;
+	stm_data->stm = stm;
+
+	err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
+	if (err)
+		goto err_device;
+
+	err = device_add(&stm->dev);
+	if (err)
+		goto err_device;
+
+	/*
+	 * Use delayed autosuspend to avoid bouncing back and forth
+	 * on recurring character device writes, with the initial
+	 * delay time of 2 seconds.
+	 */
+	pm_runtime_no_callbacks(&stm->dev);
+	pm_runtime_use_autosuspend(&stm->dev);
+	pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
+	pm_runtime_set_suspended(&stm->dev);
+	pm_runtime_enable(&stm->dev);
+
+	return 0;
+
+err_device:
+	unregister_chrdev(stm->major, stm_data->name);
+
+	/* matches device_initialize() above */
+	put_device(&stm->dev);
+err_free:
+	vfree(stm);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(stm_register_device);
+
+static int __stm_source_link_drop(struct stm_source_device *src,
+				  struct stm_device *stm);
+
+void stm_unregister_device(struct stm_data *stm_data)
+{
+	struct stm_device *stm = stm_data->stm;
+	struct stm_source_device *src, *iter;
+	int i, ret;
+
+	pm_runtime_dont_use_autosuspend(&stm->dev);
+	pm_runtime_disable(&stm->dev);
+
+	mutex_lock(&stm->link_mutex);
+	list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
+		ret = __stm_source_link_drop(src, stm);
+		/*
+		 * src <-> stm link must not change under the same
+		 * stm::link_mutex, so complain loudly if it has;
+		 * also in this situation ret!=0 means this src is
+		 * not connected to this stm and it should be otherwise
+		 * safe to proceed with the tear-down of stm.
+		 */
+		WARN_ON_ONCE(ret);
+	}
+	mutex_unlock(&stm->link_mutex);
+
+	synchronize_srcu(&stm_source_srcu);
+
+	unregister_chrdev(stm->major, stm_data->name);
+
+	mutex_lock(&stm->policy_mutex);
+	if (stm->policy)
+		stp_policy_unbind(stm->policy);
+	mutex_unlock(&stm->policy_mutex);
+
+	for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
+		stp_master_free(stm, i);
+
+	device_unregister(&stm->dev);
+	stm_data->stm = NULL;
+}
+EXPORT_SYMBOL_GPL(stm_unregister_device);
+
+/*
+ * stm::link_list access serialization uses a spinlock and a mutex; holding
+ * either of them guarantees that the list is stable; modification requires
+ * holding both of them.
+ *
+ * Lock ordering is as follows:
+ *   stm::link_mutex
+ *     stm::link_lock
+ *       src::link_lock
+ */
+
+/**
+ * stm_source_link_add() - connect an stm_source device to an stm device
+ * @src:	stm_source device
+ * @stm:	stm device
+ *
+ * This function establishes a link from stm_source to an stm device so that
+ * the former can send out trace data to the latter.
+ *
+ * Return:	0 on success, -errno otherwise.
+ */
+static int stm_source_link_add(struct stm_source_device *src,
+			       struct stm_device *stm)
+{
+	char *ids[] = { NULL, "default", NULL };
+	int err = -ENOMEM;
+
+	mutex_lock(&stm->link_mutex);
+	spin_lock(&stm->link_lock);
+	spin_lock(&src->link_lock);
+
+	/* src->link is dereferenced under stm_source_srcu but not the list */
+	rcu_assign_pointer(src->link, stm);
+	list_add_tail(&src->link_entry, &stm->link_list);
+
+	spin_unlock(&src->link_lock);
+	spin_unlock(&stm->link_lock);
+	mutex_unlock(&stm->link_mutex);
+
+	ids[0] = kstrdup(src->data->name, GFP_KERNEL);
+	if (!ids[0])
+		goto fail_detach;
+
+	err = stm_assign_first_policy(stm, &src->output, ids,
+				      src->data->nr_chans);
+	kfree(ids[0]);
+
+	if (err)
+		goto fail_detach;
+
+	/* this is to notify the STM device that a new link has been made */
+	if (stm->data->link)
+		err = stm->data->link(stm->data, src->output.master,
+				      src->output.channel);
+
+	if (err)
+		goto fail_free_output;
+
+	/* this is to let the source carry out all necessary preparations */
+	if (src->data->link)
+		src->data->link(src->data);
+
+	return 0;
+
+fail_free_output:
+	stm_output_free(stm, &src->output);
+
+fail_detach:
+	mutex_lock(&stm->link_mutex);
+	spin_lock(&stm->link_lock);
+	spin_lock(&src->link_lock);
+
+	rcu_assign_pointer(src->link, NULL);
+	list_del_init(&src->link_entry);
+
+	spin_unlock(&src->link_lock);
+	spin_unlock(&stm->link_lock);
+	mutex_unlock(&stm->link_mutex);
+
+	return err;
+}
+
+/**
+ * __stm_source_link_drop() - detach stm_source from an stm device
+ * @src:	stm_source device
+ * @stm:	stm device
+ *
+ * If @stm is @src::link, disconnect them from one another and put the
+ * reference on the @stm device.
+ *
+ * Caller must hold stm::link_mutex.
+ */
+static int __stm_source_link_drop(struct stm_source_device *src,
+				  struct stm_device *stm)
+{
+	struct stm_device *link;
+	int ret = 0;
+
+	lockdep_assert_held(&stm->link_mutex);
+
+	/* for stm::link_list modification, we hold both mutex and spinlock */
+	spin_lock(&stm->link_lock);
+	spin_lock(&src->link_lock);
+	link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
+
+	/*
+	 * The linked device may have changed since we last looked, because
+	 * we weren't holding the src::link_lock back then; if this is the
+	 * case, tell the caller to retry.
+	 */
+	if (link != stm) {
+		ret = -EAGAIN;
+		goto unlock;
+	}
+
+	stm_output_free(link, &src->output);
+	list_del_init(&src->link_entry);
+	pm_runtime_mark_last_busy(&link->dev);
+	pm_runtime_put_autosuspend(&link->dev);
+	/* matches stm_find_device() from stm_source_link_store() */
+	stm_put_device(link);
+	rcu_assign_pointer(src->link, NULL);
+
+unlock:
+	spin_unlock(&src->link_lock);
+	spin_unlock(&stm->link_lock);
+
+	/*
+	 * Call the unlink callbacks for both source and stm, when we know
+	 * that we have actually performed the unlinking.
+	 */
+	if (!ret) {
+		if (src->data->unlink)
+			src->data->unlink(src->data);
+
+		if (stm->data->unlink)
+			stm->data->unlink(stm->data, src->output.master,
+					  src->output.channel);
+	}
+
+	return ret;
+}
+
+/**
+ * stm_source_link_drop() - detach stm_source from its stm device
+ * @src:	stm_source device
+ *
+ * Unlinking means disconnecting from source's STM device; after this
+ * writes will be unsuccessful until it is linked to a new STM device.
+ *
+ * This will happen on "stm_source_link" sysfs attribute write to undo
+ * the existing link (if any), or on linked STM device's de-registration.
+ */
+static void stm_source_link_drop(struct stm_source_device *src)
+{
+	struct stm_device *stm;
+	int idx, ret;
+
+retry:
+	idx = srcu_read_lock(&stm_source_srcu);
+	/*
+	 * The stm device will be valid for the duration of this
+	 * read section, but the link may change before we grab
+	 * the src::link_lock in __stm_source_link_drop().
+	 */
+	stm = srcu_dereference(src->link, &stm_source_srcu);
+
+	ret = 0;
+	if (stm) {
+		mutex_lock(&stm->link_mutex);
+		ret = __stm_source_link_drop(src, stm);
+		mutex_unlock(&stm->link_mutex);
+	}
+
+	srcu_read_unlock(&stm_source_srcu, idx);
+
+	/* if it did change, retry */
+	if (ret == -EAGAIN)
+		goto retry;
+}
+
+static ssize_t stm_source_link_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct stm_source_device *src = to_stm_source_device(dev);
+	struct stm_device *stm;
+	int idx, ret;
+
+	idx = srcu_read_lock(&stm_source_srcu);
+	stm = srcu_dereference(src->link, &stm_source_srcu);
+	ret = sprintf(buf, "%s\n",
+		      stm ? dev_name(&stm->dev) : "<none>");
+	srcu_read_unlock(&stm_source_srcu, idx);
+
+	return ret;
+}
+
+static ssize_t stm_source_link_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct stm_source_device *src = to_stm_source_device(dev);
+	struct stm_device *link;
+	int err;
+
+	stm_source_link_drop(src);
+
+	link = stm_find_device(buf);
+	if (!link)
+		return -EINVAL;
+
+	pm_runtime_get(&link->dev);
+
+	err = stm_source_link_add(src, link);
+	if (err) {
+		pm_runtime_put_autosuspend(&link->dev);
+		/* matches the stm_find_device() above */
+		stm_put_device(link);
+	}
+
+	return err ? : count;
+}
+
+static DEVICE_ATTR_RW(stm_source_link);
+
+static struct attribute *stm_source_attrs[] = {
+	&dev_attr_stm_source_link.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(stm_source);
+
+static struct class stm_source_class = {
+	.name		= "stm_source",
+	.dev_groups	= stm_source_groups,
+};
+
+static void stm_source_device_release(struct device *dev)
+{
+	struct stm_source_device *src = to_stm_source_device(dev);
+
+	kfree(src);
+}
+
+/**
+ * stm_source_register_device() - register an stm_source device
+ * @parent:	parent device
+ * @data:	device description structure
+ *
+ * This will create a device of stm_source class that can write
+ * data to an stm device once linked.
+ *
+ * Return:	0 on success, -errno otherwise.
+ */
+int stm_source_register_device(struct device *parent,
+			       struct stm_source_data *data)
+{
+	struct stm_source_device *src;
+	int err;
+
+	if (!stm_core_up)
+		return -EPROBE_DEFER;
+
+	src = kzalloc(sizeof(*src), GFP_KERNEL);
+	if (!src)
+		return -ENOMEM;
+
+	device_initialize(&src->dev);
+	src->dev.class = &stm_source_class;
+	src->dev.parent = parent;
+	src->dev.release = stm_source_device_release;
+
+	err = kobject_set_name(&src->dev.kobj, "%s", data->name);
+	if (err)
+		goto err;
+
+	pm_runtime_no_callbacks(&src->dev);
+	pm_runtime_forbid(&src->dev);
+
+	err = device_add(&src->dev);
+	if (err)
+		goto err;
+
+	stm_output_init(&src->output);
+	spin_lock_init(&src->link_lock);
+	INIT_LIST_HEAD(&src->link_entry);
+	src->data = data;
+	data->src = src;
+
+	return 0;
+
+err:
+	put_device(&src->dev);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(stm_source_register_device);
+
+/**
+ * stm_source_unregister_device() - unregister an stm_source device
+ * @data:	device description that was used to register the device
+ *
+ * This will remove a previously created stm_source device from the system.
+ */
+void stm_source_unregister_device(struct stm_source_data *data)
+{
+	struct stm_source_device *src = data->src;
+
+	stm_source_link_drop(src);
+
+	device_unregister(&src->dev);
+}
+EXPORT_SYMBOL_GPL(stm_source_unregister_device);
+
+int notrace stm_source_write(struct stm_source_data *data,
+			     unsigned int chan,
+			     const char *buf, size_t count)
+{
+	struct stm_source_device *src = data->src;
+	struct stm_device *stm;
+	int idx;
+
+	if (!src->output.nr_chans)
+		return -ENODEV;
+
+	if (chan >= src->output.nr_chans)
+		return -EINVAL;
+
+	idx = srcu_read_lock(&stm_source_srcu);
+
+	stm = srcu_dereference(src->link, &stm_source_srcu);
+	if (stm)
+		count = stm_write(stm, &src->output, chan, buf, count);
+	else
+		count = -ENODEV;
+
+	srcu_read_unlock(&stm_source_srcu, idx);
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(stm_source_write);
+
+static int __init stm_core_init(void)
+{
+	int err;
+
+	err = class_register(&stm_class);
+	if (err)
+		return err;
+
+	err = class_register(&stm_source_class);
+	if (err)
+		goto err_stm;
+
+	err = stp_configfs_init();
+	if (err)
+		goto err_src;
+
+	init_srcu_struct(&stm_source_srcu);
+	INIT_LIST_HEAD(&stm_pdrv_head);
+	mutex_init(&stm_pdrv_mutex);
+
+	/*
+	 * So as to not confuse existing users with a requirement
+	 * to load yet another module, do it here.
+	 */
+	if (IS_ENABLED(CONFIG_STM_PROTO_BASIC))
+		(void)request_module_nowait("stm_p_basic");
+	stm_core_up++;
+
+	return 0;
+
+err_src:
+	class_unregister(&stm_source_class);
+err_stm:
+	class_unregister(&stm_class);
+
+	return err;
+}
+
+module_init(stm_core_init);
+
+static void __exit stm_core_exit(void)
+{
+	cleanup_srcu_struct(&stm_source_srcu);
+	class_unregister(&stm_source_class);
+	class_unregister(&stm_class);
+	stp_configfs_exit();
+}
+
+module_exit(stm_core_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("System Trace Module device class");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/dummy_stm.c b/drivers/hwtracing/stm/dummy_stm.c
new file mode 100644
index 0000000000..38528ffdc0
--- /dev/null
+++ b/drivers/hwtracing/stm/dummy_stm.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A dummy STM device for stm/stm_source class testing.
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * STM class implements generic infrastructure for  System Trace Module devices
+ * as defined in MIPI STPv2 specification.
+ */
+
+#undef DEBUG
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+#include <uapi/linux/stm.h>
+
+static ssize_t notrace
+dummy_stm_packet(struct stm_data *stm_data, unsigned int master,
+		 unsigned int channel, unsigned int packet, unsigned int flags,
+		 unsigned int size, const unsigned char *payload)
+{
+#ifdef DEBUG
+	u64 pl = 0;
+
+	if (payload)
+		pl = *(u64 *)payload;
+
+	if (size < 8)
+		pl &= (1ull << (size * 8)) - 1;
+	trace_printk("[%u:%u] [pkt: %x/%x] (%llx)\n", master, channel,
+		     packet, size, pl);
+#endif
+	return size;
+}
+
+#define DUMMY_STM_MAX 32
+
+static struct stm_data dummy_stm[DUMMY_STM_MAX];
+
+static int nr_dummies = 4;
+
+module_param(nr_dummies, int, 0400);
+
+static unsigned int fail_mode;
+
+module_param(fail_mode, int, 0600);
+
+static unsigned int master_min;
+
+module_param(master_min, int, 0400);
+
+static unsigned int master_max = STP_MASTER_MAX;
+
+module_param(master_max, int, 0400);
+
+static unsigned int nr_channels = STP_CHANNEL_MAX;
+
+module_param(nr_channels, int, 0400);
+
+static int dummy_stm_link(struct stm_data *data, unsigned int master,
+			  unsigned int channel)
+{
+	if (fail_mode && (channel & fail_mode))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int dummy_stm_init(void)
+{
+	int i, ret = -ENOMEM;
+
+	if (nr_dummies < 0 || nr_dummies > DUMMY_STM_MAX)
+		return -EINVAL;
+
+	if (master_min > master_max ||
+	    master_max > STP_MASTER_MAX ||
+	    nr_channels > STP_CHANNEL_MAX)
+		return -EINVAL;
+
+	for (i = 0; i < nr_dummies; i++) {
+		dummy_stm[i].name = kasprintf(GFP_KERNEL, "dummy_stm.%d", i);
+		if (!dummy_stm[i].name)
+			goto fail_unregister;
+
+		dummy_stm[i].sw_start		= master_min;
+		dummy_stm[i].sw_end		= master_max;
+		dummy_stm[i].sw_nchannels	= nr_channels;
+		dummy_stm[i].packet		= dummy_stm_packet;
+		dummy_stm[i].link		= dummy_stm_link;
+
+		ret = stm_register_device(NULL, &dummy_stm[i], THIS_MODULE);
+		if (ret)
+			goto fail_free;
+	}
+
+	return 0;
+
+fail_unregister:
+	for (i--; i >= 0; i--) {
+		stm_unregister_device(&dummy_stm[i]);
+fail_free:
+		kfree(dummy_stm[i].name);
+	}
+
+	return ret;
+
+}
+
+static void dummy_stm_exit(void)
+{
+	int i;
+
+	for (i = 0; i < nr_dummies; i++) {
+		stm_unregister_device(&dummy_stm[i]);
+		kfree(dummy_stm[i].name);
+	}
+}
+
+module_init(dummy_stm_init);
+module_exit(dummy_stm_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("dummy_stm device");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c
new file mode 100644
index 0000000000..3bb606dfa6
--- /dev/null
+++ b/drivers/hwtracing/stm/ftrace.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple kernel driver to link kernel Ftrace and an STM device
+ * Copyright (c) 2016, Linaro Ltd.
+ *
+ * STM Ftrace will be registered as a trace_export.
+ */
+
+#include <linux/module.h>
+#include <linux/stm.h>
+#include <linux/trace.h>
+
+#define STM_FTRACE_NR_CHANNELS 1
+#define STM_FTRACE_CHAN 0
+
+static int stm_ftrace_link(struct stm_source_data *data);
+static void stm_ftrace_unlink(struct stm_source_data *data);
+
+static struct stm_ftrace {
+	struct stm_source_data	data;
+	struct trace_export	ftrace;
+} stm_ftrace = {
+	.data	= {
+		.name		= "ftrace",
+		.nr_chans	= STM_FTRACE_NR_CHANNELS,
+		.link		= stm_ftrace_link,
+		.unlink		= stm_ftrace_unlink,
+	},
+};
+
+/**
+ * stm_ftrace_write() - write data to STM via 'stm_ftrace' source
+ * @buf:	buffer containing the data packet
+ * @len:	length of the data packet
+ */
+static void notrace
+stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
+{
+	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
+	/* This is called from trace system with preemption disabled */
+	unsigned int cpu = smp_processor_id();
+
+	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
+}
+
+static int stm_ftrace_link(struct stm_source_data *data)
+{
+	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
+
+	sf->ftrace.write = stm_ftrace_write;
+	sf->ftrace.flags = TRACE_EXPORT_FUNCTION | TRACE_EXPORT_EVENT
+			| TRACE_EXPORT_MARKER;
+
+	return register_ftrace_export(&sf->ftrace);
+}
+
+static void stm_ftrace_unlink(struct stm_source_data *data)
+{
+	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
+
+	unregister_ftrace_export(&sf->ftrace);
+}
+
+static int __init stm_ftrace_init(void)
+{
+	int ret;
+
+	stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
+	ret = stm_source_register_device(NULL, &stm_ftrace.data);
+	if (ret)
+		pr_err("Failed to register stm_source - ftrace.\n");
+
+	return ret;
+}
+
+static void __exit stm_ftrace_exit(void)
+{
+	stm_source_unregister_device(&stm_ftrace.data);
+}
+
+module_init(stm_ftrace_init);
+module_exit(stm_ftrace_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("stm_ftrace driver");
+MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");
diff --git a/drivers/hwtracing/stm/heartbeat.c b/drivers/hwtracing/stm/heartbeat.c
new file mode 100644
index 0000000000..81d7b21d31
--- /dev/null
+++ b/drivers/hwtracing/stm/heartbeat.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple heartbeat STM source driver
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * Heartbeat STM source will send repetitive messages over STM devices to a
+ * trace host.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/hrtimer.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+
+#define STM_HEARTBEAT_MAX	32
+
+static int nr_devs = 4;
+static int interval_ms = 10;
+
+module_param(nr_devs, int, 0400);
+module_param(interval_ms, int, 0600);
+
+static struct stm_heartbeat {
+	struct stm_source_data	data;
+	struct hrtimer		hrtimer;
+	unsigned int		active;
+} stm_heartbeat[STM_HEARTBEAT_MAX];
+
+static const char str[] = "heartbeat stm source driver is here to serve you";
+
+static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
+{
+	struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
+						       hrtimer);
+
+	stm_source_write(&heartbeat->data, 0, str, sizeof str);
+	if (heartbeat->active)
+		hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
+
+	return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
+}
+
+static int stm_heartbeat_link(struct stm_source_data *data)
+{
+	struct stm_heartbeat *heartbeat =
+		container_of(data, struct stm_heartbeat, data);
+
+	heartbeat->active = 1;
+	hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
+		      HRTIMER_MODE_ABS);
+
+	return 0;
+}
+
+static void stm_heartbeat_unlink(struct stm_source_data *data)
+{
+	struct stm_heartbeat *heartbeat =
+		container_of(data, struct stm_heartbeat, data);
+
+	heartbeat->active = 0;
+	hrtimer_cancel(&heartbeat->hrtimer);
+}
+
+static int stm_heartbeat_init(void)
+{
+	int i, ret;
+
+	if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX)
+		return -EINVAL;
+
+	for (i = 0; i < nr_devs; i++) {
+		stm_heartbeat[i].data.name =
+			kasprintf(GFP_KERNEL, "heartbeat.%d", i);
+		if (!stm_heartbeat[i].data.name) {
+			ret = -ENOMEM;
+			goto fail_unregister;
+		}
+
+		stm_heartbeat[i].data.nr_chans	= 1;
+		stm_heartbeat[i].data.link	= stm_heartbeat_link;
+		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
+		hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
+			     HRTIMER_MODE_ABS);
+		stm_heartbeat[i].hrtimer.function =
+			stm_heartbeat_hrtimer_handler;
+
+		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
+		if (ret)
+			goto fail_free;
+	}
+
+	return 0;
+
+fail_unregister:
+	for (i--; i >= 0; i--) {
+		stm_source_unregister_device(&stm_heartbeat[i].data);
+fail_free:
+		kfree(stm_heartbeat[i].data.name);
+	}
+
+	return ret;
+}
+
+static void stm_heartbeat_exit(void)
+{
+	int i;
+
+	for (i = 0; i < nr_devs; i++) {
+		stm_source_unregister_device(&stm_heartbeat[i].data);
+		kfree(stm_heartbeat[i].data.name);
+	}
+}
+
+module_init(stm_heartbeat_init);
+module_exit(stm_heartbeat_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("stm_heartbeat driver");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/p_basic.c b/drivers/hwtracing/stm/p_basic.c
new file mode 100644
index 0000000000..8980a6a5fd
--- /dev/null
+++ b/drivers/hwtracing/stm/p_basic.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Basic framing protocol for STM devices.
+ * Copyright (c) 2018, Intel Corporation.
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/stm.h>
+#include "stm.h"
+
+static ssize_t basic_write(struct stm_data *data, struct stm_output *output,
+			   unsigned int chan, const char *buf, size_t count)
+{
+	unsigned int c = output->channel + chan;
+	unsigned int m = output->master;
+	const unsigned char nil = 0;
+	ssize_t sz;
+
+	sz = stm_data_write(data, m, c, true, buf, count);
+	if (sz > 0)
+		data->packet(data, m, c, STP_PACKET_FLAG, 0, 0, &nil);
+
+	return sz;
+}
+
+static const struct stm_protocol_driver basic_pdrv = {
+	.owner	= THIS_MODULE,
+	.name	= "p_basic",
+	.write	= basic_write,
+};
+
+static int basic_stm_init(void)
+{
+	return stm_register_protocol(&basic_pdrv);
+}
+
+static void basic_stm_exit(void)
+{
+	stm_unregister_protocol(&basic_pdrv);
+}
+
+module_init(basic_stm_init);
+module_exit(basic_stm_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Basic STM framing protocol driver");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/p_sys-t.c b/drivers/hwtracing/stm/p_sys-t.c
new file mode 100644
index 0000000000..8254971c02
--- /dev/null
+++ b/drivers/hwtracing/stm/p_sys-t.c
@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MIPI SyS-T framing protocol for STM devices.
+ * Copyright (c) 2018, Intel Corporation.
+ */
+
+#include <linux/configfs.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/uuid.h>
+#include <linux/stm.h>
+#include "stm.h"
+
+enum sys_t_message_type {
+	MIPI_SYST_TYPE_BUILD	= 0,
+	MIPI_SYST_TYPE_SHORT32,
+	MIPI_SYST_TYPE_STRING,
+	MIPI_SYST_TYPE_CATALOG,
+	MIPI_SYST_TYPE_RAW	= 6,
+	MIPI_SYST_TYPE_SHORT64,
+	MIPI_SYST_TYPE_CLOCK,
+};
+
+enum sys_t_message_severity {
+	MIPI_SYST_SEVERITY_MAX	= 0,
+	MIPI_SYST_SEVERITY_FATAL,
+	MIPI_SYST_SEVERITY_ERROR,
+	MIPI_SYST_SEVERITY_WARNING,
+	MIPI_SYST_SEVERITY_INFO,
+	MIPI_SYST_SEVERITY_USER1,
+	MIPI_SYST_SEVERITY_USER2,
+	MIPI_SYST_SEVERITY_DEBUG,
+};
+
+enum sys_t_message_build_subtype {
+	MIPI_SYST_BUILD_ID_COMPACT32 = 0,
+	MIPI_SYST_BUILD_ID_COMPACT64,
+	MIPI_SYST_BUILD_ID_LONG,
+};
+
+enum sys_t_message_clock_subtype {
+	MIPI_SYST_CLOCK_TRANSPORT_SYNC = 1,
+};
+
+enum sys_t_message_string_subtype {
+	MIPI_SYST_STRING_GENERIC	= 1,
+	MIPI_SYST_STRING_FUNCTIONENTER,
+	MIPI_SYST_STRING_FUNCTIONEXIT,
+	MIPI_SYST_STRING_INVALIDPARAM	= 5,
+	MIPI_SYST_STRING_ASSERT		= 7,
+	MIPI_SYST_STRING_PRINTF_32	= 11,
+	MIPI_SYST_STRING_PRINTF_64	= 12,
+};
+
+#define MIPI_SYST_TYPE(t)		((u32)(MIPI_SYST_TYPE_ ## t))
+#define MIPI_SYST_SEVERITY(s)		((u32)(MIPI_SYST_SEVERITY_ ## s) << 4)
+#define MIPI_SYST_OPT_LOC		BIT(8)
+#define MIPI_SYST_OPT_LEN		BIT(9)
+#define MIPI_SYST_OPT_CHK		BIT(10)
+#define MIPI_SYST_OPT_TS		BIT(11)
+#define MIPI_SYST_UNIT(u)		((u32)(u) << 12)
+#define MIPI_SYST_ORIGIN(o)		((u32)(o) << 16)
+#define MIPI_SYST_OPT_GUID		BIT(23)
+#define MIPI_SYST_SUBTYPE(s)		((u32)(MIPI_SYST_ ## s) << 24)
+#define MIPI_SYST_UNITLARGE(u)		(MIPI_SYST_UNIT(u & 0xf) | \
+					 MIPI_SYST_ORIGIN(u >> 4))
+#define MIPI_SYST_TYPES(t, s)		(MIPI_SYST_TYPE(t) | \
+					 MIPI_SYST_SUBTYPE(t ## _ ## s))
+
+#define DATA_HEADER	(MIPI_SYST_TYPES(STRING, GENERIC)	| \
+			 MIPI_SYST_SEVERITY(INFO)		| \
+			 MIPI_SYST_OPT_GUID)
+
+#define CLOCK_SYNC_HEADER	(MIPI_SYST_TYPES(CLOCK, TRANSPORT_SYNC)	| \
+				 MIPI_SYST_SEVERITY(MAX))
+
+struct sys_t_policy_node {
+	uuid_t		uuid;
+	bool		do_len;
+	unsigned long	ts_interval;
+	unsigned long	clocksync_interval;
+};
+
+struct sys_t_output {
+	struct sys_t_policy_node	node;
+	unsigned long	ts_jiffies;
+	unsigned long	clocksync_jiffies;
+};
+
+static void sys_t_policy_node_init(void *priv)
+{
+	struct sys_t_policy_node *pn = priv;
+
+	uuid_gen(&pn->uuid);
+}
+
+static int sys_t_output_open(void *priv, struct stm_output *output)
+{
+	struct sys_t_policy_node *pn = priv;
+	struct sys_t_output *opriv;
+
+	opriv = kzalloc(sizeof(*opriv), GFP_ATOMIC);
+	if (!opriv)
+		return -ENOMEM;
+
+	memcpy(&opriv->node, pn, sizeof(opriv->node));
+	output->pdrv_private = opriv;
+
+	return 0;
+}
+
+static void sys_t_output_close(struct stm_output *output)
+{
+	kfree(output->pdrv_private);
+}
+
+static ssize_t sys_t_policy_uuid_show(struct config_item *item,
+				      char *page)
+{
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+
+	return sprintf(page, "%pU\n", &pn->uuid);
+}
+
+static ssize_t
+sys_t_policy_uuid_store(struct config_item *item, const char *page,
+			size_t count)
+{
+	struct mutex *mutexp = &item->ci_group->cg_subsys->su_mutex;
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+	int ret;
+
+	mutex_lock(mutexp);
+	ret = uuid_parse(page, &pn->uuid);
+	mutex_unlock(mutexp);
+
+	return ret < 0 ? ret : count;
+}
+
+CONFIGFS_ATTR(sys_t_policy_, uuid);
+
+static ssize_t sys_t_policy_do_len_show(struct config_item *item,
+				      char *page)
+{
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+
+	return sprintf(page, "%d\n", pn->do_len);
+}
+
+static ssize_t
+sys_t_policy_do_len_store(struct config_item *item, const char *page,
+			size_t count)
+{
+	struct mutex *mutexp = &item->ci_group->cg_subsys->su_mutex;
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+	int ret;
+
+	mutex_lock(mutexp);
+	ret = kstrtobool(page, &pn->do_len);
+	mutex_unlock(mutexp);
+
+	return ret ? ret : count;
+}
+
+CONFIGFS_ATTR(sys_t_policy_, do_len);
+
+static ssize_t sys_t_policy_ts_interval_show(struct config_item *item,
+					     char *page)
+{
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+
+	return sprintf(page, "%u\n", jiffies_to_msecs(pn->ts_interval));
+}
+
+static ssize_t
+sys_t_policy_ts_interval_store(struct config_item *item, const char *page,
+			       size_t count)
+{
+	struct mutex *mutexp = &item->ci_group->cg_subsys->su_mutex;
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+	unsigned int ms;
+	int ret;
+
+	mutex_lock(mutexp);
+	ret = kstrtouint(page, 10, &ms);
+	mutex_unlock(mutexp);
+
+	if (!ret) {
+		pn->ts_interval = msecs_to_jiffies(ms);
+		return count;
+	}
+
+	return ret;
+}
+
+CONFIGFS_ATTR(sys_t_policy_, ts_interval);
+
+static ssize_t sys_t_policy_clocksync_interval_show(struct config_item *item,
+						    char *page)
+{
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+
+	return sprintf(page, "%u\n", jiffies_to_msecs(pn->clocksync_interval));
+}
+
+static ssize_t
+sys_t_policy_clocksync_interval_store(struct config_item *item,
+				      const char *page, size_t count)
+{
+	struct mutex *mutexp = &item->ci_group->cg_subsys->su_mutex;
+	struct sys_t_policy_node *pn = to_pdrv_policy_node(item);
+	unsigned int ms;
+	int ret;
+
+	mutex_lock(mutexp);
+	ret = kstrtouint(page, 10, &ms);
+	mutex_unlock(mutexp);
+
+	if (!ret) {
+		pn->clocksync_interval = msecs_to_jiffies(ms);
+		return count;
+	}
+
+	return ret;
+}
+
+CONFIGFS_ATTR(sys_t_policy_, clocksync_interval);
+
+static struct configfs_attribute *sys_t_policy_attrs[] = {
+	&sys_t_policy_attr_uuid,
+	&sys_t_policy_attr_do_len,
+	&sys_t_policy_attr_ts_interval,
+	&sys_t_policy_attr_clocksync_interval,
+	NULL,
+};
+
+static inline bool sys_t_need_ts(struct sys_t_output *op)
+{
+	if (op->node.ts_interval &&
+	    time_after(jiffies, op->ts_jiffies + op->node.ts_interval)) {
+		op->ts_jiffies = jiffies;
+
+		return true;
+	}
+
+	return false;
+}
+
+static bool sys_t_need_clock_sync(struct sys_t_output *op)
+{
+	if (op->node.clocksync_interval &&
+	    time_after(jiffies,
+		       op->clocksync_jiffies + op->node.clocksync_interval)) {
+		op->clocksync_jiffies = jiffies;
+
+		return true;
+	}
+
+	return false;
+}
+
+static ssize_t
+sys_t_clock_sync(struct stm_data *data, unsigned int m, unsigned int c)
+{
+	u32 header = CLOCK_SYNC_HEADER;
+	const unsigned char nil = 0;
+	u64 payload[2]; /* Clock value and frequency */
+	ssize_t sz;
+
+	sz = data->packet(data, m, c, STP_PACKET_DATA, STP_PACKET_TIMESTAMPED,
+			  4, (u8 *)&header);
+	if (sz <= 0)
+		return sz;
+
+	payload[0] = ktime_get_real_ns();
+	payload[1] = NSEC_PER_SEC;
+	sz = stm_data_write(data, m, c, false, &payload, sizeof(payload));
+	if (sz <= 0)
+		return sz;
+
+	data->packet(data, m, c, STP_PACKET_FLAG, 0, 0, &nil);
+
+	return sizeof(header) + sizeof(payload);
+}
+
+static ssize_t sys_t_write(struct stm_data *data, struct stm_output *output,
+			   unsigned int chan, const char *buf, size_t count)
+{
+	struct sys_t_output *op = output->pdrv_private;
+	unsigned int c = output->channel + chan;
+	unsigned int m = output->master;
+	const unsigned char nil = 0;
+	u32 header = DATA_HEADER;
+	u8 uuid[UUID_SIZE];
+	ssize_t sz;
+
+	/* We require an existing policy node to proceed */
+	if (!op)
+		return -EINVAL;
+
+	if (sys_t_need_clock_sync(op)) {
+		sz = sys_t_clock_sync(data, m, c);
+		if (sz <= 0)
+			return sz;
+	}
+
+	if (op->node.do_len)
+		header |= MIPI_SYST_OPT_LEN;
+	if (sys_t_need_ts(op))
+		header |= MIPI_SYST_OPT_TS;
+
+	/*
+	 * STP framing rules for SyS-T frames:
+	 *   * the first packet of the SyS-T frame is timestamped;
+	 *   * the last packet is a FLAG.
+	 */
+	/* Message layout: HEADER / GUID / [LENGTH /][TIMESTAMP /] DATA */
+	/* HEADER */
+	sz = data->packet(data, m, c, STP_PACKET_DATA, STP_PACKET_TIMESTAMPED,
+			  4, (u8 *)&header);
+	if (sz <= 0)
+		return sz;
+
+	/* GUID */
+	export_uuid(uuid, &op->node.uuid);
+	sz = stm_data_write(data, m, c, false, uuid, sizeof(op->node.uuid));
+	if (sz <= 0)
+		return sz;
+
+	/* [LENGTH] */
+	if (op->node.do_len) {
+		u16 length = count;
+
+		sz = data->packet(data, m, c, STP_PACKET_DATA, 0, 2,
+				  (u8 *)&length);
+		if (sz <= 0)
+			return sz;
+	}
+
+	/* [TIMESTAMP] */
+	if (header & MIPI_SYST_OPT_TS) {
+		u64 ts = ktime_get_real_ns();
+
+		sz = stm_data_write(data, m, c, false, &ts, sizeof(ts));
+		if (sz <= 0)
+			return sz;
+	}
+
+	/* DATA */
+	sz = stm_data_write(data, m, c, false, buf, count);
+	if (sz > 0)
+		data->packet(data, m, c, STP_PACKET_FLAG, 0, 0, &nil);
+
+	return sz;
+}
+
+static const struct stm_protocol_driver sys_t_pdrv = {
+	.owner			= THIS_MODULE,
+	.name			= "p_sys-t",
+	.priv_sz		= sizeof(struct sys_t_policy_node),
+	.write			= sys_t_write,
+	.policy_attr		= sys_t_policy_attrs,
+	.policy_node_init	= sys_t_policy_node_init,
+	.output_open		= sys_t_output_open,
+	.output_close		= sys_t_output_close,
+};
+
+static int sys_t_stm_init(void)
+{
+	return stm_register_protocol(&sys_t_pdrv);
+}
+
+static void sys_t_stm_exit(void)
+{
+	stm_unregister_protocol(&sys_t_pdrv);
+}
+
+module_init(sys_t_stm_init);
+module_exit(sys_t_stm_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MIPI SyS-T STM framing protocol driver");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
new file mode 100644
index 0000000000..42103c3a17
--- /dev/null
+++ b/drivers/hwtracing/stm/policy.c
@@ -0,0 +1,570 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Trace Module (STM) master/channel allocation policy management
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * A master/channel allocation policy allows mapping string identifiers to
+ * master and channel ranges, where allocation can be done.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/configfs.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+#include "stm.h"
+
+/*
+ * STP Master/Channel allocation policy configfs layout.
+ */
+
+struct stp_policy {
+	struct config_group	group;
+	struct stm_device	*stm;
+};
+
+struct stp_policy_node {
+	struct config_group	group;
+	struct stp_policy	*policy;
+	unsigned int		first_master;
+	unsigned int		last_master;
+	unsigned int		first_channel;
+	unsigned int		last_channel;
+	/* this is the one that's exposed to the attributes */
+	unsigned char		priv[];
+};
+
+void *stp_policy_node_priv(struct stp_policy_node *pn)
+{
+	if (!pn)
+		return NULL;
+
+	return pn->priv;
+}
+
+static struct configfs_subsystem stp_policy_subsys;
+
+void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
+				unsigned int *mstart, unsigned int *mend,
+				unsigned int *cstart, unsigned int *cend)
+{
+	*mstart	= policy_node->first_master;
+	*mend	= policy_node->last_master;
+	*cstart	= policy_node->first_channel;
+	*cend	= policy_node->last_channel;
+}
+
+static inline struct stp_policy *to_stp_policy(struct config_item *item)
+{
+	return item ?
+		container_of(to_config_group(item), struct stp_policy, group) :
+		NULL;
+}
+
+static inline struct stp_policy_node *
+to_stp_policy_node(struct config_item *item)
+{
+	return item ?
+		container_of(to_config_group(item), struct stp_policy_node,
+			     group) :
+		NULL;
+}
+
+void *to_pdrv_policy_node(struct config_item *item)
+{
+	struct stp_policy_node *node = to_stp_policy_node(item);
+
+	return stp_policy_node_priv(node);
+}
+EXPORT_SYMBOL_GPL(to_pdrv_policy_node);
+
+static ssize_t
+stp_policy_node_masters_show(struct config_item *item, char *page)
+{
+	struct stp_policy_node *policy_node = to_stp_policy_node(item);
+	ssize_t count;
+
+	count = sprintf(page, "%u %u\n", policy_node->first_master,
+			policy_node->last_master);
+
+	return count;
+}
+
+static ssize_t
+stp_policy_node_masters_store(struct config_item *item, const char *page,
+			      size_t count)
+{
+	struct stp_policy_node *policy_node = to_stp_policy_node(item);
+	unsigned int first, last;
+	struct stm_device *stm;
+	char *p = (char *)page;
+	ssize_t ret = -ENODEV;
+
+	if (sscanf(p, "%u %u", &first, &last) != 2)
+		return -EINVAL;
+
+	mutex_lock(&stp_policy_subsys.su_mutex);
+	stm = policy_node->policy->stm;
+	if (!stm)
+		goto unlock;
+
+	/* must be within [sw_start..sw_end], which is an inclusive range */
+	if (first > last || first < stm->data->sw_start ||
+	    last > stm->data->sw_end) {
+		ret = -ERANGE;
+		goto unlock;
+	}
+
+	ret = count;
+	policy_node->first_master = first;
+	policy_node->last_master = last;
+
+unlock:
+	mutex_unlock(&stp_policy_subsys.su_mutex);
+
+	return ret;
+}
+
+static ssize_t
+stp_policy_node_channels_show(struct config_item *item, char *page)
+{
+	struct stp_policy_node *policy_node = to_stp_policy_node(item);
+	ssize_t count;
+
+	count = sprintf(page, "%u %u\n", policy_node->first_channel,
+			policy_node->last_channel);
+
+	return count;
+}
+
+static ssize_t
+stp_policy_node_channels_store(struct config_item *item, const char *page,
+			       size_t count)
+{
+	struct stp_policy_node *policy_node = to_stp_policy_node(item);
+	unsigned int first, last;
+	struct stm_device *stm;
+	char *p = (char *)page;
+	ssize_t ret = -ENODEV;
+
+	if (sscanf(p, "%u %u", &first, &last) != 2)
+		return -EINVAL;
+
+	mutex_lock(&stp_policy_subsys.su_mutex);
+	stm = policy_node->policy->stm;
+	if (!stm)
+		goto unlock;
+
+	if (first > INT_MAX || last > INT_MAX || first > last ||
+	    last >= stm->data->sw_nchannels) {
+		ret = -ERANGE;
+		goto unlock;
+	}
+
+	ret = count;
+	policy_node->first_channel = first;
+	policy_node->last_channel = last;
+
+unlock:
+	mutex_unlock(&stp_policy_subsys.su_mutex);
+
+	return ret;
+}
+
+static void stp_policy_node_release(struct config_item *item)
+{
+	struct stp_policy_node *node = to_stp_policy_node(item);
+
+	kfree(node);
+}
+
+static struct configfs_item_operations stp_policy_node_item_ops = {
+	.release		= stp_policy_node_release,
+};
+
+CONFIGFS_ATTR(stp_policy_node_, masters);
+CONFIGFS_ATTR(stp_policy_node_, channels);
+
+static struct configfs_attribute *stp_policy_node_attrs[] = {
+	&stp_policy_node_attr_masters,
+	&stp_policy_node_attr_channels,
+	NULL,
+};
+
+static const struct config_item_type stp_policy_type;
+static const struct config_item_type stp_policy_node_type;
+
+const struct config_item_type *
+get_policy_node_type(struct configfs_attribute **attrs)
+{
+	struct config_item_type *type;
+	struct configfs_attribute **merged;
+
+	type = kmemdup(&stp_policy_node_type, sizeof(stp_policy_node_type),
+		       GFP_KERNEL);
+	if (!type)
+		return NULL;
+
+	merged = memcat_p(stp_policy_node_attrs, attrs);
+	if (!merged) {
+		kfree(type);
+		return NULL;
+	}
+
+	type->ct_attrs = merged;
+
+	return type;
+}
+
+static struct config_group *
+stp_policy_node_make(struct config_group *group, const char *name)
+{
+	const struct config_item_type *type = &stp_policy_node_type;
+	struct stp_policy_node *policy_node, *parent_node;
+	const struct stm_protocol_driver *pdrv;
+	struct stp_policy *policy;
+
+	if (group->cg_item.ci_type == &stp_policy_type) {
+		policy = container_of(group, struct stp_policy, group);
+	} else {
+		parent_node = container_of(group, struct stp_policy_node,
+					   group);
+		policy = parent_node->policy;
+	}
+
+	if (!policy->stm)
+		return ERR_PTR(-ENODEV);
+
+	pdrv = policy->stm->pdrv;
+	policy_node =
+		kzalloc(offsetof(struct stp_policy_node, priv[pdrv->priv_sz]),
+			GFP_KERNEL);
+	if (!policy_node)
+		return ERR_PTR(-ENOMEM);
+
+	if (pdrv->policy_node_init)
+		pdrv->policy_node_init((void *)policy_node->priv);
+
+	if (policy->stm->pdrv_node_type)
+		type = policy->stm->pdrv_node_type;
+
+	config_group_init_type_name(&policy_node->group, name, type);
+
+	policy_node->policy = policy;
+
+	/* default values for the attributes */
+	policy_node->first_master = policy->stm->data->sw_start;
+	policy_node->last_master = policy->stm->data->sw_end;
+	policy_node->first_channel = 0;
+	policy_node->last_channel = policy->stm->data->sw_nchannels - 1;
+
+	return &policy_node->group;
+}
+
+static void
+stp_policy_node_drop(struct config_group *group, struct config_item *item)
+{
+	config_item_put(item);
+}
+
+static struct configfs_group_operations stp_policy_node_group_ops = {
+	.make_group	= stp_policy_node_make,
+	.drop_item	= stp_policy_node_drop,
+};
+
+static const struct config_item_type stp_policy_node_type = {
+	.ct_item_ops	= &stp_policy_node_item_ops,
+	.ct_group_ops	= &stp_policy_node_group_ops,
+	.ct_attrs	= stp_policy_node_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+/*
+ * Root group: policies.
+ */
+static ssize_t stp_policy_device_show(struct config_item *item,
+				      char *page)
+{
+	struct stp_policy *policy = to_stp_policy(item);
+	ssize_t count;
+
+	count = sprintf(page, "%s\n",
+			(policy && policy->stm) ?
+			policy->stm->data->name :
+			"<none>");
+
+	return count;
+}
+
+CONFIGFS_ATTR_RO(stp_policy_, device);
+
+static ssize_t stp_policy_protocol_show(struct config_item *item,
+					char *page)
+{
+	struct stp_policy *policy = to_stp_policy(item);
+	ssize_t count;
+
+	count = sprintf(page, "%s\n",
+			(policy && policy->stm) ?
+			policy->stm->pdrv->name :
+			"<none>");
+
+	return count;
+}
+
+CONFIGFS_ATTR_RO(stp_policy_, protocol);
+
+static struct configfs_attribute *stp_policy_attrs[] = {
+	&stp_policy_attr_device,
+	&stp_policy_attr_protocol,
+	NULL,
+};
+
+void stp_policy_unbind(struct stp_policy *policy)
+{
+	struct stm_device *stm = policy->stm;
+
+	/*
+	 * stp_policy_release() will not call here if the policy is already
+	 * unbound; other users should not either, as no link exists between
+	 * this policy and anything else in that case
+	 */
+	if (WARN_ON_ONCE(!policy->stm))
+		return;
+
+	lockdep_assert_held(&stm->policy_mutex);
+
+	stm->policy = NULL;
+	policy->stm = NULL;
+
+	/*
+	 * Drop the reference on the protocol driver and lose the link.
+	 */
+	stm_put_protocol(stm->pdrv);
+	stm->pdrv = NULL;
+	stm_put_device(stm);
+}
+
+static void stp_policy_release(struct config_item *item)
+{
+	struct stp_policy *policy = to_stp_policy(item);
+	struct stm_device *stm = policy->stm;
+
+	/* a policy *can* be unbound and still exist in configfs tree */
+	if (!stm)
+		return;
+
+	mutex_lock(&stm->policy_mutex);
+	stp_policy_unbind(policy);
+	mutex_unlock(&stm->policy_mutex);
+
+	kfree(policy);
+}
+
+static struct configfs_item_operations stp_policy_item_ops = {
+	.release		= stp_policy_release,
+};
+
+static struct configfs_group_operations stp_policy_group_ops = {
+	.make_group	= stp_policy_node_make,
+};
+
+static const struct config_item_type stp_policy_type = {
+	.ct_item_ops	= &stp_policy_item_ops,
+	.ct_group_ops	= &stp_policy_group_ops,
+	.ct_attrs	= stp_policy_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group *
+stp_policy_make(struct config_group *group, const char *name)
+{
+	const struct config_item_type *pdrv_node_type;
+	const struct stm_protocol_driver *pdrv;
+	char *devname, *proto, *p;
+	struct config_group *ret;
+	struct stm_device *stm;
+	int err;
+
+	devname = kasprintf(GFP_KERNEL, "%s", name);
+	if (!devname)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * node must look like <device_name>.<policy_name>, where
+	 * <device_name> is the name of an existing stm device; may
+	 *               contain dots;
+	 * <policy_name> is an arbitrary string; may not contain dots
+	 * <device_name>:<protocol_name>.<policy_name>
+	 */
+	p = strrchr(devname, '.');
+	if (!p) {
+		kfree(devname);
+		return ERR_PTR(-EINVAL);
+	}
+
+	*p = '\0';
+
+	/*
+	 * look for ":<protocol_name>":
+	 *  + no protocol suffix: fall back to whatever is available;
+	 *  + unknown protocol: fail the whole thing
+	 */
+	proto = strrchr(devname, ':');
+	if (proto)
+		*proto++ = '\0';
+
+	stm = stm_find_device(devname);
+	if (!stm) {
+		kfree(devname);
+		return ERR_PTR(-ENODEV);
+	}
+
+	err = stm_lookup_protocol(proto, &pdrv, &pdrv_node_type);
+	kfree(devname);
+
+	if (err) {
+		stm_put_device(stm);
+		return ERR_PTR(-ENODEV);
+	}
+
+	mutex_lock(&stm->policy_mutex);
+	if (stm->policy) {
+		ret = ERR_PTR(-EBUSY);
+		goto unlock_policy;
+	}
+
+	stm->policy = kzalloc(sizeof(*stm->policy), GFP_KERNEL);
+	if (!stm->policy) {
+		ret = ERR_PTR(-ENOMEM);
+		goto unlock_policy;
+	}
+
+	config_group_init_type_name(&stm->policy->group, name,
+				    &stp_policy_type);
+
+	stm->pdrv = pdrv;
+	stm->pdrv_node_type = pdrv_node_type;
+	stm->policy->stm = stm;
+	ret = &stm->policy->group;
+
+unlock_policy:
+	mutex_unlock(&stm->policy_mutex);
+
+	if (IS_ERR(ret)) {
+		/*
+		 * pdrv and stm->pdrv at this point can be quite different,
+		 * and only one of them needs to be 'put'
+		 */
+		stm_put_protocol(pdrv);
+		stm_put_device(stm);
+	}
+
+	return ret;
+}
+
+static struct configfs_group_operations stp_policy_root_group_ops = {
+	.make_group	= stp_policy_make,
+};
+
+static const struct config_item_type stp_policy_root_type = {
+	.ct_group_ops	= &stp_policy_root_group_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem stp_policy_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf	= "stp-policy",
+			.ci_type	= &stp_policy_root_type,
+		},
+	},
+};
+
+/*
+ * Lock the policy mutex from the outside
+ */
+static struct stp_policy_node *
+__stp_policy_node_lookup(struct stp_policy *policy, char *s)
+{
+	struct stp_policy_node *policy_node, *ret = NULL;
+	struct list_head *head = &policy->group.cg_children;
+	struct config_item *item;
+	char *start, *end = s;
+
+	if (list_empty(head))
+		return NULL;
+
+next:
+	for (;;) {
+		start = strsep(&end, "/");
+		if (!start)
+			break;
+
+		if (!*start)
+			continue;
+
+		list_for_each_entry(item, head, ci_entry) {
+			policy_node = to_stp_policy_node(item);
+
+			if (!strcmp(start,
+				    policy_node->group.cg_item.ci_name)) {
+				ret = policy_node;
+
+				if (!end)
+					goto out;
+
+				head = &policy_node->group.cg_children;
+				goto next;
+			}
+		}
+		break;
+	}
+
+out:
+	return ret;
+}
+
+
+struct stp_policy_node *
+stp_policy_node_lookup(struct stm_device *stm, char *s)
+{
+	struct stp_policy_node *policy_node = NULL;
+
+	mutex_lock(&stp_policy_subsys.su_mutex);
+
+	mutex_lock(&stm->policy_mutex);
+	if (stm->policy)
+		policy_node = __stp_policy_node_lookup(stm->policy, s);
+	mutex_unlock(&stm->policy_mutex);
+
+	if (policy_node)
+		config_item_get(&policy_node->group.cg_item);
+	else
+		mutex_unlock(&stp_policy_subsys.su_mutex);
+
+	return policy_node;
+}
+
+void stp_policy_node_put(struct stp_policy_node *policy_node)
+{
+	lockdep_assert_held(&stp_policy_subsys.su_mutex);
+
+	mutex_unlock(&stp_policy_subsys.su_mutex);
+	config_item_put(&policy_node->group.cg_item);
+}
+
+int __init stp_configfs_init(void)
+{
+	config_group_init(&stp_policy_subsys.su_group);
+	mutex_init(&stp_policy_subsys.su_mutex);
+	return configfs_register_subsystem(&stp_policy_subsys);
+}
+
+void __exit stp_configfs_exit(void)
+{
+	configfs_unregister_subsystem(&stp_policy_subsys);
+}
diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h
new file mode 100644
index 0000000000..a9be49fc7a
--- /dev/null
+++ b/drivers/hwtracing/stm/stm.h
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * System Trace Module (STM) infrastructure
+ * Copyright (c) 2014, Intel Corporation.
+ *
+ * STM class implements generic infrastructure for  System Trace Module devices
+ * as defined in MIPI STPv2 specification.
+ */
+
+#ifndef _STM_STM_H_
+#define _STM_STM_H_
+
+#include <linux/configfs.h>
+
+struct stp_policy;
+struct stp_policy_node;
+struct stm_protocol_driver;
+
+int stp_configfs_init(void);
+void stp_configfs_exit(void);
+
+void *stp_policy_node_priv(struct stp_policy_node *pn);
+
+struct stp_master {
+	unsigned int	nr_free;
+	unsigned long	chan_map[];
+};
+
+struct stm_device {
+	struct device		dev;
+	struct module		*owner;
+	struct stp_policy	*policy;
+	struct mutex		policy_mutex;
+	int			major;
+	unsigned int		sw_nmasters;
+	struct stm_data		*data;
+	struct mutex		link_mutex;
+	spinlock_t		link_lock;
+	struct list_head	link_list;
+	/* framing protocol in use */
+	const struct stm_protocol_driver	*pdrv;
+	const struct config_item_type		*pdrv_node_type;
+	/* master allocation */
+	spinlock_t		mc_lock;
+	struct stp_master	*masters[];
+};
+
+#define to_stm_device(_d)				\
+	container_of((_d), struct stm_device, dev)
+
+struct stp_policy_node *
+stp_policy_node_lookup(struct stm_device *stm, char *s);
+void stp_policy_node_put(struct stp_policy_node *policy_node);
+void stp_policy_unbind(struct stp_policy *policy);
+
+void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
+				unsigned int *mstart, unsigned int *mend,
+				unsigned int *cstart, unsigned int *cend);
+
+const struct config_item_type *
+get_policy_node_type(struct configfs_attribute **attrs);
+
+struct stm_output {
+	spinlock_t		lock;
+	unsigned int		master;
+	unsigned int		channel;
+	unsigned int		nr_chans;
+	void			*pdrv_private;
+};
+
+struct stm_file {
+	struct stm_device	*stm;
+	struct stm_output	output;
+};
+
+struct stm_device *stm_find_device(const char *name);
+void stm_put_device(struct stm_device *stm);
+
+struct stm_source_device {
+	struct device		dev;
+	struct stm_source_data	*data;
+	spinlock_t		link_lock;
+	struct stm_device __rcu	*link;
+	struct list_head	link_entry;
+	/* one output per stm_source device */
+	struct stm_output	output;
+};
+
+#define to_stm_source_device(_d)				\
+	container_of((_d), struct stm_source_device, dev)
+
+void *to_pdrv_policy_node(struct config_item *item);
+
+struct stm_protocol_driver {
+	struct module	*owner;
+	const char	*name;
+	ssize_t		(*write)(struct stm_data *data,
+				 struct stm_output *output, unsigned int chan,
+				 const char *buf, size_t count);
+	void		(*policy_node_init)(void *arg);
+	int		(*output_open)(void *priv, struct stm_output *output);
+	void		(*output_close)(struct stm_output *output);
+	ssize_t		priv_sz;
+	struct configfs_attribute	**policy_attr;
+};
+
+int stm_register_protocol(const struct stm_protocol_driver *pdrv);
+void stm_unregister_protocol(const struct stm_protocol_driver *pdrv);
+int stm_lookup_protocol(const char *name,
+			const struct stm_protocol_driver **pdrv,
+			const struct config_item_type **type);
+void stm_put_protocol(const struct stm_protocol_driver *pdrv);
+ssize_t stm_data_write(struct stm_data *data, unsigned int m,
+		       unsigned int c, bool ts_first, const void *buf,
+		       size_t count);
+
+#endif /* _STM_STM_H_ */