123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231 |
- /*
- * isochronous resources helper functions
- *
- * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
- * Licensed under the terms of the GNU General Public License, version 2.
- */
- #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 = fw_parent_device(r->unit)->card;
- int bandwidth, channel;
- 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);
|