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ALSA: virtio: handling control and I/O messages for the PCM device

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The driver implements a message-based transport for I/O substream
operations. Before the start of the substream, the hardware buffer is
sliced into I/O messages, the number of which is equal to the current
number of periods. The size of each message is equal to the current
size of one period.

I/O messages are organized in an ordered queue. The completion of the
I/O message indicates an elapsed period (the only exception is the end
of the stream for the capture substream). Upon completion, the message
is automatically re-added to the end of the queue.

Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
Link: https://lore.kernel.org/r/20210302164709.3142702-6-anton.yakovlev@opensynergy.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Anton Yakovlev 2021-03-02 17:47:05 +01:00 committed by Takashi Iwai
parent 29b96bf50b
commit f40a28679e
6 changed files with 515 additions and 5 deletions
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3
sound/virtio/Makefile
View File

@ -5,5 +5,6 @@ obj-$(CONFIG_SND_VIRTIO) += virtio_snd.o
virtio_snd-objs := \
virtio_card.o \
virtio_ctl_msg.o \
virtio_pcm.o
virtio_pcm.o \
virtio_pcm_msg.o

22
sound/virtio/virtio_card.c
View File

@ -55,6 +55,12 @@ static void virtsnd_event_send(struct virtqueue *vqueue,
static void virtsnd_event_dispatch(struct virtio_snd *snd,
struct virtio_snd_event *event)
{
switch (le32_to_cpu(event->hdr.code)) {
case VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED:
case VIRTIO_SND_EVT_PCM_XRUN:
virtsnd_pcm_event(snd, event);
break;
}
}
/**
@ -101,11 +107,15 @@ static int virtsnd_find_vqs(struct virtio_snd *snd)
struct virtio_device *vdev = snd->vdev;
static vq_callback_t *callbacks[VIRTIO_SND_VQ_MAX] = {
[VIRTIO_SND_VQ_CONTROL] = virtsnd_ctl_notify_cb,
[VIRTIO_SND_VQ_EVENT] = virtsnd_event_notify_cb
[VIRTIO_SND_VQ_EVENT] = virtsnd_event_notify_cb,
[VIRTIO_SND_VQ_TX] = virtsnd_pcm_tx_notify_cb,
[VIRTIO_SND_VQ_RX] = virtsnd_pcm_rx_notify_cb
};
static const char *names[VIRTIO_SND_VQ_MAX] = {
[VIRTIO_SND_VQ_CONTROL] = "virtsnd-ctl",
[VIRTIO_SND_VQ_EVENT] = "virtsnd-event"
[VIRTIO_SND_VQ_EVENT] = "virtsnd-event",
[VIRTIO_SND_VQ_TX] = "virtsnd-tx",
[VIRTIO_SND_VQ_RX] = "virtsnd-rx"
};
struct virtqueue *vqs[VIRTIO_SND_VQ_MAX] = { 0 };
unsigned int i;
@ -318,8 +328,12 @@ static void virtsnd_remove(struct virtio_device *vdev)
vdev->config->del_vqs(vdev);
vdev->config->reset(vdev);
for (i = 0; snd->substreams && i < snd->nsubstreams; ++i)
cancel_work_sync(&snd->substreams[i].elapsed_period);
for (i = 0; snd->substreams && i < snd->nsubstreams; ++i) {
struct virtio_pcm_substream *vss = &snd->substreams[i];
cancel_work_sync(&vss->elapsed_period);
virtsnd_pcm_msg_free(vss);
}
kfree(snd->event_msgs);
}

9
sound/virtio/virtio_card.h
View File

@ -79,4 +79,13 @@ virtsnd_rx_queue(struct virtio_snd *snd)
return &snd->queues[VIRTIO_SND_VQ_RX];
}
static inline struct virtio_snd_queue *
virtsnd_pcm_queue(struct virtio_pcm_substream *vss)
{
if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK)
return virtsnd_tx_queue(vss->snd);
else
return virtsnd_rx_queue(vss->snd);
}
#endif /* VIRTIO_SND_CARD_H */

32
sound/virtio/virtio_pcm.c
View File

@ -353,6 +353,8 @@ int virtsnd_pcm_parse_cfg(struct virtio_snd *snd)
vss->snd = snd;
vss->sid = i;
INIT_WORK(&vss->elapsed_period, virtsnd_pcm_period_elapsed);
init_waitqueue_head(&vss->msg_empty);
spin_lock_init(&vss->lock);
rc = virtsnd_pcm_build_hw(vss, &info[i]);
if (rc)
@ -477,3 +479,33 @@ int virtsnd_pcm_build_devs(struct virtio_snd *snd)
return 0;
}
/**
* virtsnd_pcm_event() - Handle the PCM device event notification.
* @snd: VirtIO sound device.
* @event: VirtIO sound event.
*
* Context: Interrupt context.
*/
void virtsnd_pcm_event(struct virtio_snd *snd, struct virtio_snd_event *event)
{
struct virtio_pcm_substream *vss;
u32 sid = le32_to_cpu(event->data);
if (sid >= snd->nsubstreams)
return;
vss = &snd->substreams[sid];
switch (le32_to_cpu(event->hdr.code)) {
case VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED:
/* TODO: deal with shmem elapsed period */
break;
case VIRTIO_SND_EVT_PCM_XRUN:
spin_lock(&vss->lock);
if (vss->xfer_enabled)
vss->xfer_xrun = true;
spin_unlock(&vss->lock);
break;
}
}

40
sound/virtio/virtio_pcm.h
View File

@ -23,6 +23,17 @@ struct virtio_pcm_msg;
* @substream: Kernel ALSA substream.
* @hw: Kernel ALSA substream hardware descriptor.
* @elapsed_period: Kernel work to handle the elapsed period state.
* @lock: Spinlock that protects fields shared by interrupt handlers and
* substream operators.
* @buffer_bytes: Current buffer size in bytes.
* @hw_ptr: Substream hardware pointer value in bytes [0 ... buffer_bytes).
* @xfer_enabled: Data transfer state (0 - off, 1 - on).
* @xfer_xrun: Data underflow/overflow state (0 - no xrun, 1 - xrun).
* @msgs: Allocated I/O messages.
* @nmsgs: Number of allocated I/O messages.
* @msg_last_enqueued: Index of the last I/O message added to the virtqueue.
* @msg_count: Number of pending I/O messages in the virtqueue.
* @msg_empty: Notify when msg_count is zero.
*/
struct virtio_pcm_substream {
struct virtio_snd *snd;
@ -33,6 +44,16 @@ struct virtio_pcm_substream {
struct snd_pcm_substream *substream;
struct snd_pcm_hardware hw;
struct work_struct elapsed_period;
spinlock_t lock;
size_t buffer_bytes;
size_t hw_ptr;
bool xfer_enabled;
bool xfer_xrun;
struct virtio_pcm_msg **msgs;
unsigned int nmsgs;
int msg_last_enqueued;
unsigned int msg_count;
wait_queue_head_t msg_empty;
};
/**
@ -65,8 +86,27 @@ int virtsnd_pcm_parse_cfg(struct virtio_snd *snd);
int virtsnd_pcm_build_devs(struct virtio_snd *snd);
void virtsnd_pcm_event(struct virtio_snd *snd, struct virtio_snd_event *event);
void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue);
void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue);
struct virtio_pcm *virtsnd_pcm_find(struct virtio_snd *snd, u32 nid);
struct virtio_pcm *virtsnd_pcm_find_or_create(struct virtio_snd *snd, u32 nid);
struct virtio_snd_msg *
virtsnd_pcm_ctl_msg_alloc(struct virtio_pcm_substream *vss,
unsigned int command, gfp_t gfp);
int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss,
unsigned int periods, unsigned int period_bytes);
void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss);
int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss);
unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss);
#endif /* VIRTIO_SND_PCM_H */

414
sound/virtio/virtio_pcm_msg.c Normal file
View File

@ -0,0 +1,414 @@
// SPDX-License-Identifier: GPL-2.0+
/*
* virtio-snd: Virtio sound device
* Copyright (C) 2021 OpenSynergy GmbH
*/
#include <sound/pcm_params.h>
#include "virtio_card.h"
/**
* struct virtio_pcm_msg - VirtIO I/O message.
* @substream: VirtIO PCM substream.
* @xfer: Request header payload.
* @status: Response header payload.
* @length: Data length in bytes.
* @sgs: Payload scatter-gather table.
*/
struct virtio_pcm_msg {
struct virtio_pcm_substream *substream;
struct virtio_snd_pcm_xfer xfer;
struct virtio_snd_pcm_status status;
size_t length;
struct scatterlist sgs[0];
};
/**
* enum pcm_msg_sg_index - Index values for the virtio_pcm_msg->sgs field in
* an I/O message.
* @PCM_MSG_SG_XFER: Element containing a virtio_snd_pcm_xfer structure.
* @PCM_MSG_SG_STATUS: Element containing a virtio_snd_pcm_status structure.
* @PCM_MSG_SG_DATA: The first element containing a data buffer.
*/
enum pcm_msg_sg_index {
PCM_MSG_SG_XFER = 0,
PCM_MSG_SG_STATUS,
PCM_MSG_SG_DATA
};
/**
* virtsnd_pcm_sg_num() - Count the number of sg-elements required to represent
* vmalloc'ed buffer.
* @data: Pointer to vmalloc'ed buffer.
* @length: Buffer size.
*
* Context: Any context.
* Return: Number of physically contiguous parts in the @data.
*/
static int virtsnd_pcm_sg_num(u8 *data, unsigned int length)
{
phys_addr_t sg_address;
unsigned int sg_length;
int num = 0;
while (length) {
struct page *pg = vmalloc_to_page(data);
phys_addr_t pg_address = page_to_phys(pg);
size_t pg_length;
pg_length = PAGE_SIZE - offset_in_page(data);
if (pg_length > length)
pg_length = length;
if (!num || sg_address + sg_length != pg_address) {
sg_address = pg_address;
sg_length = pg_length;
num++;
} else {
sg_length += pg_length;
}
data += pg_length;
length -= pg_length;
}
return num;
}
/**
* virtsnd_pcm_sg_from() - Build sg-list from vmalloc'ed buffer.
* @sgs: Preallocated sg-list to populate.
* @nsgs: The maximum number of elements in the @sgs.
* @data: Pointer to vmalloc'ed buffer.
* @length: Buffer size.
*
* Splits the buffer into physically contiguous parts and makes an sg-list of
* such parts.
*
* Context: Any context.
*/
static void virtsnd_pcm_sg_from(struct scatterlist *sgs, int nsgs, u8 *data,
unsigned int length)
{
int idx = -1;
while (length) {
struct page *pg = vmalloc_to_page(data);
size_t pg_length;
pg_length = PAGE_SIZE - offset_in_page(data);
if (pg_length > length)
pg_length = length;
if (idx == -1 ||
sg_phys(&sgs[idx]) + sgs[idx].length != page_to_phys(pg)) {
if (idx + 1 == nsgs)
break;
sg_set_page(&sgs[++idx], pg, pg_length,
offset_in_page(data));
} else {
sgs[idx].length += pg_length;
}
data += pg_length;
length -= pg_length;
}
sg_mark_end(&sgs[idx]);
}
/**
* virtsnd_pcm_msg_alloc() - Allocate I/O messages.
* @vss: VirtIO PCM substream.
* @periods: Current number of periods.
* @period_bytes: Current period size in bytes.
*
* The function slices the buffer into @periods parts (each with the size of
* @period_bytes), and creates @periods corresponding I/O messages.
*
* Context: Any context that permits to sleep.
* Return: 0 on success, -ENOMEM on failure.
*/
int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss,
unsigned int periods, unsigned int period_bytes)
{
struct snd_pcm_runtime *runtime = vss->substream->runtime;
unsigned int i;
vss->msgs = kcalloc(periods, sizeof(*vss->msgs), GFP_KERNEL);
if (!vss->msgs)
return -ENOMEM;
vss->nmsgs = periods;
for (i = 0; i < periods; ++i) {
u8 *data = runtime->dma_area + period_bytes * i;
int sg_num = virtsnd_pcm_sg_num(data, period_bytes);
struct virtio_pcm_msg *msg;
msg = kzalloc(sizeof(*msg) + sizeof(*msg->sgs) * (sg_num + 2),
GFP_KERNEL);
if (!msg)
return -ENOMEM;
msg->substream = vss;
sg_init_one(&msg->sgs[PCM_MSG_SG_XFER], &msg->xfer,
sizeof(msg->xfer));
sg_init_one(&msg->sgs[PCM_MSG_SG_STATUS], &msg->status,
sizeof(msg->status));
msg->length = period_bytes;
virtsnd_pcm_sg_from(&msg->sgs[PCM_MSG_SG_DATA], sg_num, data,
period_bytes);
vss->msgs[i] = msg;
}
return 0;
}
/**
* virtsnd_pcm_msg_free() - Free all allocated I/O messages.
* @vss: VirtIO PCM substream.
*
* Context: Any context.
*/
void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss)
{
unsigned int i;
for (i = 0; vss->msgs && i < vss->nmsgs; ++i)
kfree(vss->msgs[i]);
kfree(vss->msgs);
vss->msgs = NULL;
vss->nmsgs = 0;
}
/**
* virtsnd_pcm_msg_send() - Send asynchronous I/O messages.
* @vss: VirtIO PCM substream.
*
* All messages are organized in an ordered circular list. Each time the
* function is called, all currently non-enqueued messages are added to the
* virtqueue. For this, the function keeps track of two values:
*
* msg_last_enqueued = index of the last enqueued message,
* msg_count = # of pending messages in the virtqueue.
*
* Context: Any context. Expects the tx/rx queue and the VirtIO substream
* spinlocks to be held by caller.
* Return: 0 on success, -errno on failure.
*/
int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss)
{
struct snd_pcm_runtime *runtime = vss->substream->runtime;
struct virtio_snd *snd = vss->snd;
struct virtio_device *vdev = snd->vdev;
struct virtqueue *vqueue = virtsnd_pcm_queue(vss)->vqueue;
int i;
int n;
bool notify = false;
i = (vss->msg_last_enqueued + 1) % runtime->periods;
n = runtime->periods - vss->msg_count;
for (; n; --n, i = (i + 1) % runtime->periods) {
struct virtio_pcm_msg *msg = vss->msgs[i];
struct scatterlist *psgs[] = {
&msg->sgs[PCM_MSG_SG_XFER],
&msg->sgs[PCM_MSG_SG_DATA],
&msg->sgs[PCM_MSG_SG_STATUS]
};
int rc;
msg->xfer.stream_id = cpu_to_le32(vss->sid);
memset(&msg->status, 0, sizeof(msg->status));
if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK)
rc = virtqueue_add_sgs(vqueue, psgs, 2, 1, msg,
GFP_ATOMIC);
else
rc = virtqueue_add_sgs(vqueue, psgs, 1, 2, msg,
GFP_ATOMIC);
if (rc) {
dev_err(&vdev->dev,
"SID %u: failed to send I/O message\n",
vss->sid);
return rc;
}
vss->msg_last_enqueued = i;
vss->msg_count++;
}
if (!(vss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING)))
notify = virtqueue_kick_prepare(vqueue);
if (notify)
virtqueue_notify(vqueue);
return 0;
}
/**
* virtsnd_pcm_msg_pending_num() - Returns the number of pending I/O messages.
* @vss: VirtIO substream.
*
* Context: Any context.
* Return: Number of messages.
*/
unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss)
{
unsigned int num;
unsigned long flags;
spin_lock_irqsave(&vss->lock, flags);
num = vss->msg_count;
spin_unlock_irqrestore(&vss->lock, flags);
return num;
}
/**
* virtsnd_pcm_msg_complete() - Complete an I/O message.
* @msg: I/O message.
* @written_bytes: Number of bytes written to the message.
*
* Completion of the message means the elapsed period. If transmission is
* allowed, then each completed message is immediately placed back at the end
* of the queue.
*
* For the playback substream, @written_bytes is equal to sizeof(msg->status).
*
* For the capture substream, @written_bytes is equal to sizeof(msg->status)
* plus the number of captured bytes.
*
* Context: Interrupt context. Takes and releases the VirtIO substream spinlock.
*/
static void virtsnd_pcm_msg_complete(struct virtio_pcm_msg *msg,
size_t written_bytes)
{
struct virtio_pcm_substream *vss = msg->substream;
/*
* hw_ptr always indicates the buffer position of the first I/O message
* in the virtqueue. Therefore, on each completion of an I/O message,
* the hw_ptr value is unconditionally advanced.
*/
spin_lock(&vss->lock);
/*
* If the capture substream returned an incorrect status, then just
* increase the hw_ptr by the message size.
*/
if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK ||
written_bytes <= sizeof(msg->status))
vss->hw_ptr += msg->length;
else
vss->hw_ptr += written_bytes - sizeof(msg->status);
if (vss->hw_ptr >= vss->buffer_bytes)
vss->hw_ptr -= vss->buffer_bytes;
vss->xfer_xrun = false;
vss->msg_count--;
if (vss->xfer_enabled) {
struct snd_pcm_runtime *runtime = vss->substream->runtime;
runtime->delay =
bytes_to_frames(runtime,
le32_to_cpu(msg->status.latency_bytes));
schedule_work(&vss->elapsed_period);
virtsnd_pcm_msg_send(vss);
} else if (!vss->msg_count) {
wake_up_all(&vss->msg_empty);
}
spin_unlock(&vss->lock);
}
/**
* virtsnd_pcm_notify_cb() - Process all completed I/O messages.
* @queue: Underlying tx/rx virtqueue.
*
* Context: Interrupt context. Takes and releases the tx/rx queue spinlock.
*/
static inline void virtsnd_pcm_notify_cb(struct virtio_snd_queue *queue)
{
struct virtio_pcm_msg *msg;
u32 written_bytes;
unsigned long flags;
spin_lock_irqsave(&queue->lock, flags);
do {
virtqueue_disable_cb(queue->vqueue);
while ((msg = virtqueue_get_buf(queue->vqueue, &written_bytes)))
virtsnd_pcm_msg_complete(msg, written_bytes);
if (unlikely(virtqueue_is_broken(queue->vqueue)))
break;
} while (!virtqueue_enable_cb(queue->vqueue));
spin_unlock_irqrestore(&queue->lock, flags);
}
/**
* virtsnd_pcm_tx_notify_cb() - Process all completed TX messages.
* @vqueue: Underlying tx virtqueue.
*
* Context: Interrupt context.
*/
void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue)
{
struct virtio_snd *snd = vqueue->vdev->priv;
virtsnd_pcm_notify_cb(virtsnd_tx_queue(snd));
}
/**
* virtsnd_pcm_rx_notify_cb() - Process all completed RX messages.
* @vqueue: Underlying rx virtqueue.
*
* Context: Interrupt context.
*/
void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue)
{
struct virtio_snd *snd = vqueue->vdev->priv;
virtsnd_pcm_notify_cb(virtsnd_rx_queue(snd));
}
/**
* virtsnd_pcm_ctl_msg_alloc() - Allocate and initialize the PCM device control
* message for the specified substream.
* @vss: VirtIO PCM substream.
* @command: Control request code (VIRTIO_SND_R_PCM_XXX).
* @gfp: Kernel flags for memory allocation.
*
* Context: Any context. May sleep if @gfp flags permit.
* Return: Allocated message on success, NULL on failure.
*/
struct virtio_snd_msg *
virtsnd_pcm_ctl_msg_alloc(struct virtio_pcm_substream *vss,
unsigned int command, gfp_t gfp)
{
size_t request_size = sizeof(struct virtio_snd_pcm_hdr);
size_t response_size = sizeof(struct virtio_snd_hdr);
struct virtio_snd_msg *msg;
switch (command) {
case VIRTIO_SND_R_PCM_SET_PARAMS:
request_size = sizeof(struct virtio_snd_pcm_set_params);
break;
}
msg = virtsnd_ctl_msg_alloc(request_size, response_size, gfp);
if (msg) {
struct virtio_snd_pcm_hdr *hdr = virtsnd_ctl_msg_request(msg);
hdr->hdr.code = cpu_to_le32(command);
hdr->stream_id = cpu_to_le32(vss->sid);
}
return msg;
}