237 lines
6.5 KiB
C
237 lines
6.5 KiB
C
/*
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* isochronous resources helper functions
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*
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* Copyright (c) Clemens Ladisch <clemens@ladisch.de>
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* Licensed under the terms of the GNU General Public License, version 2.
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*/
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#include <linux/device.h>
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#include <linux/firewire.h>
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#include <linux/firewire-constants.h>
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#include <linux/export.h>
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#include <linux/jiffies.h>
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#include <linux/mutex.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include "iso-resources.h"
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/**
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* fw_iso_resources_init - initializes a &struct fw_iso_resources
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* @r: the resource manager to initialize
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* @unit: the device unit for which the resources will be needed
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*
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* If the device does not support all channel numbers, change @r->channels_mask
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* after calling this function.
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*/
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int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
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{
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r->channels_mask = ~0uLL;
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r->unit = unit;
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mutex_init(&r->mutex);
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r->allocated = false;
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return 0;
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}
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EXPORT_SYMBOL(fw_iso_resources_init);
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/**
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* fw_iso_resources_destroy - destroy a resource manager
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* @r: the resource manager that is no longer needed
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*/
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void fw_iso_resources_destroy(struct fw_iso_resources *r)
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{
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WARN_ON(r->allocated);
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mutex_destroy(&r->mutex);
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}
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EXPORT_SYMBOL(fw_iso_resources_destroy);
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static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed)
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{
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unsigned int bytes, s400_bytes;
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/* iso packets have three header quadlets and quadlet-aligned payload */
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bytes = 3 * 4 + ALIGN(max_payload_bytes, 4);
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/* convert to bandwidth units (quadlets at S1600 = bytes at S400) */
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if (speed <= SCODE_400)
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s400_bytes = bytes * (1 << (SCODE_400 - speed));
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else
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s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400));
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return s400_bytes;
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}
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static int current_bandwidth_overhead(struct fw_card *card)
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{
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/*
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* Under the usual pessimistic assumption (cable length 4.5 m), the
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* isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or
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* 88.3 + N * 24.3 in bandwidth units.
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*
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* The calculation below tries to deduce N from the current gap count.
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* If the gap count has been optimized by measuring the actual packet
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* transmission time, this derived overhead should be near the actual
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* overhead as well.
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*/
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return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512;
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}
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static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card)
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{
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for (;;) {
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s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64();
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if (delay <= 0)
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return 0;
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if (schedule_timeout_interruptible(delay) > 0)
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return -ERESTARTSYS;
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}
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}
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/**
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* fw_iso_resources_allocate - allocate isochronous channel and bandwidth
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* @r: the resource manager
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* @max_payload_bytes: the amount of data (including CIP headers) per packet
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* @speed: the speed (e.g., SCODE_400) at which the packets will be sent
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*
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* This function allocates one isochronous channel and enough bandwidth for the
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* specified packet size.
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*
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* Returns the channel number that the caller must use for streaming, or
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* a negative error code. Due to potentionally long delays, this function is
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* interruptible and can return -ERESTARTSYS. On success, the caller is
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* responsible for calling fw_iso_resources_update() on bus resets, and
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* fw_iso_resources_free() when the resources are not longer needed.
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*/
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int fw_iso_resources_allocate(struct fw_iso_resources *r,
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unsigned int max_payload_bytes, int speed)
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{
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struct fw_card *card = fw_parent_device(r->unit)->card;
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int bandwidth, channel, err;
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if (WARN_ON(r->allocated))
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return -EBADFD;
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r->bandwidth = packet_bandwidth(max_payload_bytes, speed);
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retry_after_bus_reset:
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spin_lock_irq(&card->lock);
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r->generation = card->generation;
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r->bandwidth_overhead = current_bandwidth_overhead(card);
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spin_unlock_irq(&card->lock);
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err = wait_isoch_resource_delay_after_bus_reset(card);
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if (err < 0)
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return err;
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mutex_lock(&r->mutex);
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bandwidth = r->bandwidth + r->bandwidth_overhead;
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fw_iso_resource_manage(card, r->generation, r->channels_mask,
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&channel, &bandwidth, true);
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if (channel == -EAGAIN) {
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mutex_unlock(&r->mutex);
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goto retry_after_bus_reset;
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}
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if (channel >= 0) {
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r->channel = channel;
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r->allocated = true;
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} else {
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if (channel == -EBUSY)
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dev_err(&r->unit->device,
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"isochronous resources exhausted\n");
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else
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dev_err(&r->unit->device,
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"isochronous resource allocation failed\n");
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}
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mutex_unlock(&r->mutex);
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return channel;
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}
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EXPORT_SYMBOL(fw_iso_resources_allocate);
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/**
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* fw_iso_resources_update - update resource allocations after a bus reset
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* @r: the resource manager
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*
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* This function must be called from the driver's .update handler to reallocate
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* any resources that were allocated before the bus reset. It is safe to call
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* this function if no resources are currently allocated.
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*
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* Returns a negative error code on failure. If this happens, the caller must
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* stop streaming.
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*/
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int fw_iso_resources_update(struct fw_iso_resources *r)
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{
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struct fw_card *card = fw_parent_device(r->unit)->card;
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int bandwidth, channel;
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mutex_lock(&r->mutex);
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if (!r->allocated) {
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mutex_unlock(&r->mutex);
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return 0;
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}
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spin_lock_irq(&card->lock);
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r->generation = card->generation;
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r->bandwidth_overhead = current_bandwidth_overhead(card);
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spin_unlock_irq(&card->lock);
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bandwidth = r->bandwidth + r->bandwidth_overhead;
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fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
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&channel, &bandwidth, true);
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/*
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* When another bus reset happens, pretend that the allocation
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* succeeded; we will try again for the new generation later.
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*/
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if (channel < 0 && channel != -EAGAIN) {
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r->allocated = false;
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if (channel == -EBUSY)
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dev_err(&r->unit->device,
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"isochronous resources exhausted\n");
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else
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dev_err(&r->unit->device,
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"isochronous resource allocation failed\n");
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}
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mutex_unlock(&r->mutex);
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return channel;
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}
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EXPORT_SYMBOL(fw_iso_resources_update);
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/**
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* fw_iso_resources_free - frees allocated resources
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* @r: the resource manager
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*
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* This function deallocates the channel and bandwidth, if allocated.
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*/
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void fw_iso_resources_free(struct fw_iso_resources *r)
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{
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struct fw_card *card;
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int bandwidth, channel;
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/* Not initialized. */
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if (r->unit == NULL)
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return;
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card = fw_parent_device(r->unit)->card;
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mutex_lock(&r->mutex);
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if (r->allocated) {
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bandwidth = r->bandwidth + r->bandwidth_overhead;
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fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
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&channel, &bandwidth, false);
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if (channel < 0)
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dev_err(&r->unit->device,
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"isochronous resource deallocation failed\n");
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r->allocated = false;
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}
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mutex_unlock(&r->mutex);
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}
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EXPORT_SYMBOL(fw_iso_resources_free);
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