diff options
Diffstat (limited to 'sound/firewire/iso-resources.c')
| -rw-r--r-- | sound/firewire/iso-resources.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/sound/firewire/iso-resources.c b/sound/firewire/iso-resources.c new file mode 100644 index 000000000000..6f2b5f8651fd --- /dev/null +++ b/sound/firewire/iso-resources.c @@ -0,0 +1,224 @@ +/* + * 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. + */ +void 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; +} + +/** + * 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, r->buffer); + 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, r->buffer); + /* + * 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, r->buffer); + if (channel < 0) + dev_err(&r->unit->device, + "isochronous resource deallocation failed\n"); + + r->allocated = false; + } + + mutex_unlock(&r->mutex); +} |
