1 files changed, 236 insertions, 0 deletions
diff --git a/sound/firewire/iso-resources.c b/sound/firewire/iso-resources.c
new file mode 100644
index 000000000..84f71b2ea
--- /dev/null
+++ b/sound/firewire/iso-resources.c
@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * isochronous resources helper functions
+ *
+ * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
+ */
+
+#include <linux/device.h>
+#include <linux/firewire.h>
+#include <linux/firewire-constants.h>
+#include <linux/export.h>
+#include <linux/jiffies.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include "iso-resources.h"
+
+/**
+ * fw_iso_resources_init - initializes a &struct fw_iso_resources
+ * @r: the resource manager to initialize
+ * @unit: the device unit for which the resources will be needed
+ *
+ * If the device does not support all channel numbers, change @r->channels_mask
+ * after calling this function.
+ */
+int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
+{
+	r->channels_mask = ~0uLL;
+	r->unit = unit;
+	mutex_init(&r->mutex);
+	r->allocated = false;
+
+	return 0;
+}
+EXPORT_SYMBOL(fw_iso_resources_init);
+
+/**
+ * fw_iso_resources_destroy - destroy a resource manager
+ * @r: the resource manager that is no longer needed
+ */
+void fw_iso_resources_destroy(struct fw_iso_resources *r)
+{
+	WARN_ON(r->allocated);
+	mutex_destroy(&r->mutex);
+}
+EXPORT_SYMBOL(fw_iso_resources_destroy);
+
+static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed)
+{
+	unsigned int bytes, s400_bytes;
+
+	/* iso packets have three header quadlets and quadlet-aligned payload */
+	bytes = 3 * 4 + ALIGN(max_payload_bytes, 4);
+
+	/* convert to bandwidth units (quadlets at S1600 = bytes at S400) */
+	if (speed <= SCODE_400)
+		s400_bytes = bytes * (1 << (SCODE_400 - speed));
+	else
+		s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400));
+
+	return s400_bytes;
+}
+
+static int current_bandwidth_overhead(struct fw_card *card)
+{
+	/*
+	 * Under the usual pessimistic assumption (cable length 4.5 m), the
+	 * isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or
+	 * 88.3 + N * 24.3 in bandwidth units.
+	 *
+	 * The calculation below tries to deduce N from the current gap count.
+	 * If the gap count has been optimized by measuring the actual packet
+	 * transmission time, this derived overhead should be near the actual
+	 * overhead as well.
+	 */
+	return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512;
+}
+
+static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card)
+{
+	for (;;) {
+		s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64();
+		if (delay <= 0)
+			return 0;
+		if (schedule_timeout_interruptible(delay) > 0)
+			return -ERESTARTSYS;
+	}
+}
+
+/**
+ * fw_iso_resources_allocate - allocate isochronous channel and bandwidth
+ * @r: the resource manager
+ * @max_payload_bytes: the amount of data (including CIP headers) per packet
+ * @speed: the speed (e.g., SCODE_400) at which the packets will be sent
+ *
+ * This function allocates one isochronous channel and enough bandwidth for the
+ * specified packet size.
+ *
+ * Returns the channel number that the caller must use for streaming, or
+ * a negative error code.  Due to potentionally long delays, this function is
+ * interruptible and can return -ERESTARTSYS.  On success, the caller is
+ * responsible for calling fw_iso_resources_update() on bus resets, and
+ * fw_iso_resources_free() when the resources are not longer needed.
+ */
+int fw_iso_resources_allocate(struct fw_iso_resources *r,
+			      unsigned int max_payload_bytes, int speed)
+{
+	struct fw_card *card = fw_parent_device(r->unit)->card;
+	int bandwidth, channel, err;
+
+	if (WARN_ON(r->allocated))
+		return -EBADFD;
+
+	r->bandwidth = packet_bandwidth(max_payload_bytes, speed);
+
+retry_after_bus_reset:
+	spin_lock_irq(&card->lock);
+	r->generation = card->generation;
+	r->bandwidth_overhead = current_bandwidth_overhead(card);
+	spin_unlock_irq(&card->lock);
+
+	err = wait_isoch_resource_delay_after_bus_reset(card);
+	if (err < 0)
+		return err;
+
+	mutex_lock(&r->mutex);
+
+	bandwidth = r->bandwidth + r->bandwidth_overhead;
+	fw_iso_resource_manage(card, r->generation, r->channels_mask,
+			       &channel, &bandwidth, true);
+	if (channel == -EAGAIN) {
+		mutex_unlock(&r->mutex);
+		goto retry_after_bus_reset;
+	}
+	if (channel >= 0) {
+		r->channel = channel;
+		r->allocated = true;
+	} else {
+		if (channel == -EBUSY)
+			dev_err(&r->unit->device,
+				"isochronous resources exhausted\n");
+		else
+			dev_err(&r->unit->device,
+				"isochronous resource allocation failed\n");
+	}
+
+	mutex_unlock(&r->mutex);
+
+	return channel;
+}
+EXPORT_SYMBOL(fw_iso_resources_allocate);
+
+/**
+ * fw_iso_resources_update - update resource allocations after a bus reset
+ * @r: the resource manager
+ *
+ * This function must be called from the driver's .update handler to reallocate
+ * any resources that were allocated before the bus reset.  It is safe to call
+ * this function if no resources are currently allocated.
+ *
+ * Returns a negative error code on failure.  If this happens, the caller must
+ * stop streaming.
+ */
+int fw_iso_resources_update(struct fw_iso_resources *r)
+{
+	struct fw_card *card = fw_parent_device(r->unit)->card;
+	int bandwidth, channel;
+
+	mutex_lock(&r->mutex);
+
+	if (!r->allocated) {
+		mutex_unlock(&r->mutex);
+		return 0;
+	}
+
+	spin_lock_irq(&card->lock);
+	r->generation = card->generation;
+	r->bandwidth_overhead = current_bandwidth_overhead(card);
+	spin_unlock_irq(&card->lock);
+
+	bandwidth = r->bandwidth + r->bandwidth_overhead;
+
+	fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
+			       &channel, &bandwidth, true);
+	/*
+	 * When another bus reset happens, pretend that the allocation
+	 * succeeded; we will try again for the new generation later.
+	 */
+	if (channel < 0 && channel != -EAGAIN) {
+		r->allocated = false;
+		if (channel == -EBUSY)
+			dev_err(&r->unit->device,
+				"isochronous resources exhausted\n");
+		else
+			dev_err(&r->unit->device,
+				"isochronous resource allocation failed\n");
+	}
+
+	mutex_unlock(&r->mutex);
+
+	return channel;
+}
+EXPORT_SYMBOL(fw_iso_resources_update);
+
+/**
+ * fw_iso_resources_free - frees allocated resources
+ * @r: the resource manager
+ *
+ * This function deallocates the channel and bandwidth, if allocated.
+ */
+void fw_iso_resources_free(struct fw_iso_resources *r)
+{
+	struct fw_card *card;
+	int bandwidth, channel;
+
+	/* Not initialized. */
+	if (r->unit == NULL)
+		return;
+	card = fw_parent_device(r->unit)->card;
+
+	mutex_lock(&r->mutex);
+
+	if (r->allocated) {
+		bandwidth = r->bandwidth + r->bandwidth_overhead;
+		fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
+				       &channel, &bandwidth, false);
+		if (channel < 0)
+			dev_err(&r->unit->device,
+				"isochronous resource deallocation failed\n");
+
+		r->allocated = false;
+	}
+
+	mutex_unlock(&r->mutex);
+}
+EXPORT_SYMBOL(fw_iso_resources_free);