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/*
* 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/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 = fw_unit_get(unit);
mutex_init(&r->mutex);
r->allocated = false;
return 0;
}
/**
* 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);
fw_unit_put(r->unit);
}
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;
}
/**
* 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;
}
/**
* 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);
}
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