1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * virtio-snd: Virtio sound device
4 * Copyright (C) 2021 OpenSynergy GmbH
5 */
6#include <sound/pcm_params.h>
7
8#include "virtio_card.h"
9
10/**
11 * struct virtio_pcm_msg - VirtIO I/O message.
12 * @substream: VirtIO PCM substream.
13 * @xfer: Request header payload.
14 * @status: Response header payload.
15 * @length: Data length in bytes.
16 * @sgs: Payload scatter-gather table.
17 */
18struct virtio_pcm_msg {
19	struct virtio_pcm_substream *substream;
20	struct virtio_snd_pcm_xfer xfer;
21	struct virtio_snd_pcm_status status;
22	size_t length;
23	struct scatterlist sgs[];
24};
25
26/**
27 * enum pcm_msg_sg_index - Index values for the virtio_pcm_msg->sgs field in
28 *                         an I/O message.
29 * @PCM_MSG_SG_XFER: Element containing a virtio_snd_pcm_xfer structure.
30 * @PCM_MSG_SG_STATUS: Element containing a virtio_snd_pcm_status structure.
31 * @PCM_MSG_SG_DATA: The first element containing a data buffer.
32 */
33enum pcm_msg_sg_index {
34	PCM_MSG_SG_XFER = 0,
35	PCM_MSG_SG_STATUS,
36	PCM_MSG_SG_DATA
37};
38
39/**
40 * virtsnd_pcm_sg_num() - Count the number of sg-elements required to represent
41 *                        vmalloc'ed buffer.
42 * @data: Pointer to vmalloc'ed buffer.
43 * @length: Buffer size.
44 *
45 * Context: Any context.
46 * Return: Number of physically contiguous parts in the @data.
47 */
48static int virtsnd_pcm_sg_num(u8 *data, unsigned int length)
49{
50	phys_addr_t sg_address;
51	unsigned int sg_length;
52	int num = 0;
53
54	while (length) {
55		struct page *pg = vmalloc_to_page(data);
56		phys_addr_t pg_address = page_to_phys(pg);
57		size_t pg_length;
58
59		pg_length = PAGE_SIZE - offset_in_page(data);
60		if (pg_length > length)
61			pg_length = length;
62
63		if (!num || sg_address + sg_length != pg_address) {
64			sg_address = pg_address;
65			sg_length = pg_length;
66			num++;
67		} else {
68			sg_length += pg_length;
69		}
70
71		data += pg_length;
72		length -= pg_length;
73	}
74
75	return num;
76}
77
78/**
79 * virtsnd_pcm_sg_from() - Build sg-list from vmalloc'ed buffer.
80 * @sgs: Preallocated sg-list to populate.
81 * @nsgs: The maximum number of elements in the @sgs.
82 * @data: Pointer to vmalloc'ed buffer.
83 * @length: Buffer size.
84 *
85 * Splits the buffer into physically contiguous parts and makes an sg-list of
86 * such parts.
87 *
88 * Context: Any context.
89 */
90static void virtsnd_pcm_sg_from(struct scatterlist *sgs, int nsgs, u8 *data,
91				unsigned int length)
92{
93	int idx = -1;
94
95	while (length) {
96		struct page *pg = vmalloc_to_page(data);
97		size_t pg_length;
98
99		pg_length = PAGE_SIZE - offset_in_page(data);
100		if (pg_length > length)
101			pg_length = length;
102
103		if (idx == -1 ||
104		    sg_phys(&sgs[idx]) + sgs[idx].length != page_to_phys(pg)) {
105			if (idx + 1 == nsgs)
106				break;
107			sg_set_page(&sgs[++idx], pg, pg_length,
108				    offset_in_page(data));
109		} else {
110			sgs[idx].length += pg_length;
111		}
112
113		data += pg_length;
114		length -= pg_length;
115	}
116
117	sg_mark_end(&sgs[idx]);
118}
119
120/**
121 * virtsnd_pcm_msg_alloc() - Allocate I/O messages.
122 * @vss: VirtIO PCM substream.
123 * @periods: Current number of periods.
124 * @period_bytes: Current period size in bytes.
125 *
126 * The function slices the buffer into @periods parts (each with the size of
127 * @period_bytes), and creates @periods corresponding I/O messages.
128 *
129 * Context: Any context that permits to sleep.
130 * Return: 0 on success, -ENOMEM on failure.
131 */
132int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss,
133			  unsigned int periods, unsigned int period_bytes)
134{
135	struct snd_pcm_runtime *runtime = vss->substream->runtime;
136	unsigned int i;
137
138	vss->msgs = kcalloc(periods, sizeof(*vss->msgs), GFP_KERNEL);
139	if (!vss->msgs)
140		return -ENOMEM;
141
142	vss->nmsgs = periods;
143
144	for (i = 0; i < periods; ++i) {
145		u8 *data = runtime->dma_area + period_bytes * i;
146		int sg_num = virtsnd_pcm_sg_num(data, period_bytes);
147		struct virtio_pcm_msg *msg;
148
149		msg = kzalloc(struct_size(msg, sgs, sg_num + 2), GFP_KERNEL);
150		if (!msg)
151			return -ENOMEM;
152
153		msg->substream = vss;
154		sg_init_one(&msg->sgs[PCM_MSG_SG_XFER], &msg->xfer,
155			    sizeof(msg->xfer));
156		sg_init_one(&msg->sgs[PCM_MSG_SG_STATUS], &msg->status,
157			    sizeof(msg->status));
158		virtsnd_pcm_sg_from(&msg->sgs[PCM_MSG_SG_DATA], sg_num, data,
159				    period_bytes);
160
161		vss->msgs[i] = msg;
162	}
163
164	return 0;
165}
166
167/**
168 * virtsnd_pcm_msg_free() - Free all allocated I/O messages.
169 * @vss: VirtIO PCM substream.
170 *
171 * Context: Any context.
172 */
173void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss)
174{
175	unsigned int i;
176
177	for (i = 0; vss->msgs && i < vss->nmsgs; ++i)
178		kfree(vss->msgs[i]);
179	kfree(vss->msgs);
180
181	vss->msgs = NULL;
182	vss->nmsgs = 0;
183}
184
185/**
186 * virtsnd_pcm_msg_send() - Send asynchronous I/O messages.
187 * @vss: VirtIO PCM substream.
188 * @offset: starting position that has been updated
189 * @bytes: number of bytes that has been updated
190 *
191 * All messages are organized in an ordered circular list. Each time the
192 * function is called, all currently non-enqueued messages are added to the
193 * virtqueue. For this, the function uses offset and bytes to calculate the
194 * messages that need to be added.
195 *
196 * Context: Any context. Expects the tx/rx queue and the VirtIO substream
197 *          spinlocks to be held by caller.
198 * Return: 0 on success, -errno on failure.
199 */
200int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss, unsigned long offset,
201			 unsigned long bytes)
202{
203	struct virtio_snd *snd = vss->snd;
204	struct virtio_device *vdev = snd->vdev;
205	struct virtqueue *vqueue = virtsnd_pcm_queue(vss)->vqueue;
206	unsigned long period_bytes = snd_pcm_lib_period_bytes(vss->substream);
207	unsigned long start, end, i;
208	unsigned int msg_count = vss->msg_count;
209	bool notify = false;
210	int rc;
211
212	start = offset / period_bytes;
213	end = (offset + bytes - 1) / period_bytes;
214
215	for (i = start; i <= end; i++) {
216		struct virtio_pcm_msg *msg = vss->msgs[i];
217		struct scatterlist *psgs[] = {
218			&msg->sgs[PCM_MSG_SG_XFER],
219			&msg->sgs[PCM_MSG_SG_DATA],
220			&msg->sgs[PCM_MSG_SG_STATUS]
221		};
222		unsigned long n;
223
224		n = period_bytes - (offset % period_bytes);
225		if (n > bytes)
226			n = bytes;
227
228		msg->length += n;
229		if (msg->length == period_bytes) {
230			msg->xfer.stream_id = cpu_to_le32(vss->sid);
231			memset(&msg->status, 0, sizeof(msg->status));
232
233			if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK)
234				rc = virtqueue_add_sgs(vqueue, psgs, 2, 1, msg,
235						       GFP_ATOMIC);
236			else
237				rc = virtqueue_add_sgs(vqueue, psgs, 1, 2, msg,
238						       GFP_ATOMIC);
239
240			if (rc) {
241				dev_err(&vdev->dev,
242					"SID %u: failed to send I/O message\n",
243					vss->sid);
244				return rc;
245			}
246
247			vss->msg_count++;
248		}
249
250		offset = 0;
251		bytes -= n;
252	}
253
254	if (msg_count == vss->msg_count)
255		return 0;
256
257	if (!(vss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING)))
258		notify = virtqueue_kick_prepare(vqueue);
259
260	if (notify)
261		virtqueue_notify(vqueue);
262
263	return 0;
264}
265
266/**
267 * virtsnd_pcm_msg_pending_num() - Returns the number of pending I/O messages.
268 * @vss: VirtIO substream.
269 *
270 * Context: Any context.
271 * Return: Number of messages.
272 */
273unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss)
274{
275	unsigned int num;
276	unsigned long flags;
277
278	spin_lock_irqsave(&vss->lock, flags);
279	num = vss->msg_count;
280	spin_unlock_irqrestore(&vss->lock, flags);
281
282	return num;
283}
284
285/**
286 * virtsnd_pcm_msg_complete() - Complete an I/O message.
287 * @msg: I/O message.
288 * @written_bytes: Number of bytes written to the message.
289 *
290 * Completion of the message means the elapsed period. If transmission is
291 * allowed, then each completed message is immediately placed back at the end
292 * of the queue.
293 *
294 * For the playback substream, @written_bytes is equal to sizeof(msg->status).
295 *
296 * For the capture substream, @written_bytes is equal to sizeof(msg->status)
297 * plus the number of captured bytes.
298 *
299 * Context: Interrupt context. Takes and releases the VirtIO substream spinlock.
300 */
301static void virtsnd_pcm_msg_complete(struct virtio_pcm_msg *msg,
302				     size_t written_bytes)
303{
304	struct virtio_pcm_substream *vss = msg->substream;
305
306	/*
307	 * hw_ptr always indicates the buffer position of the first I/O message
308	 * in the virtqueue. Therefore, on each completion of an I/O message,
309	 * the hw_ptr value is unconditionally advanced.
310	 */
311	spin_lock(&vss->lock);
312	/*
313	 * If the capture substream returned an incorrect status, then just
314	 * increase the hw_ptr by the message size.
315	 */
316	if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK ||
317	    written_bytes <= sizeof(msg->status))
318		vss->hw_ptr += msg->length;
319	else
320		vss->hw_ptr += written_bytes - sizeof(msg->status);
321
322	if (vss->hw_ptr >= vss->buffer_bytes)
323		vss->hw_ptr -= vss->buffer_bytes;
324
325	msg->length = 0;
326
327	vss->xfer_xrun = false;
328	vss->msg_count--;
329
330	if (vss->xfer_enabled) {
331		struct snd_pcm_runtime *runtime = vss->substream->runtime;
332
333		runtime->delay =
334			bytes_to_frames(runtime,
335					le32_to_cpu(msg->status.latency_bytes));
336
337		schedule_work(&vss->elapsed_period);
338	} else if (!vss->msg_count) {
339		wake_up_all(&vss->msg_empty);
340	}
341	spin_unlock(&vss->lock);
342}
343
344/**
345 * virtsnd_pcm_notify_cb() - Process all completed I/O messages.
346 * @queue: Underlying tx/rx virtqueue.
347 *
348 * Context: Interrupt context. Takes and releases the tx/rx queue spinlock.
349 */
350static inline void virtsnd_pcm_notify_cb(struct virtio_snd_queue *queue)
351{
352	struct virtio_pcm_msg *msg;
353	u32 written_bytes;
354	unsigned long flags;
355
356	spin_lock_irqsave(&queue->lock, flags);
357	do {
358		virtqueue_disable_cb(queue->vqueue);
359		while ((msg = virtqueue_get_buf(queue->vqueue, &written_bytes)))
360			virtsnd_pcm_msg_complete(msg, written_bytes);
361	} while (!virtqueue_enable_cb(queue->vqueue));
362	spin_unlock_irqrestore(&queue->lock, flags);
363}
364
365/**
366 * virtsnd_pcm_tx_notify_cb() - Process all completed TX messages.
367 * @vqueue: Underlying tx virtqueue.
368 *
369 * Context: Interrupt context.
370 */
371void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue)
372{
373	struct virtio_snd *snd = vqueue->vdev->priv;
374
375	virtsnd_pcm_notify_cb(virtsnd_tx_queue(snd));
376}
377
378/**
379 * virtsnd_pcm_rx_notify_cb() - Process all completed RX messages.
380 * @vqueue: Underlying rx virtqueue.
381 *
382 * Context: Interrupt context.
383 */
384void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue)
385{
386	struct virtio_snd *snd = vqueue->vdev->priv;
387
388	virtsnd_pcm_notify_cb(virtsnd_rx_queue(snd));
389}
390
391/**
392 * virtsnd_pcm_ctl_msg_alloc() - Allocate and initialize the PCM device control
393 *                               message for the specified substream.
394 * @vss: VirtIO PCM substream.
395 * @command: Control request code (VIRTIO_SND_R_PCM_XXX).
396 * @gfp: Kernel flags for memory allocation.
397 *
398 * Context: Any context. May sleep if @gfp flags permit.
399 * Return: Allocated message on success, NULL on failure.
400 */
401struct virtio_snd_msg *
402virtsnd_pcm_ctl_msg_alloc(struct virtio_pcm_substream *vss,
403			  unsigned int command, gfp_t gfp)
404{
405	size_t request_size = sizeof(struct virtio_snd_pcm_hdr);
406	size_t response_size = sizeof(struct virtio_snd_hdr);
407	struct virtio_snd_msg *msg;
408
409	switch (command) {
410	case VIRTIO_SND_R_PCM_SET_PARAMS:
411		request_size = sizeof(struct virtio_snd_pcm_set_params);
412		break;
413	}
414
415	msg = virtsnd_ctl_msg_alloc(request_size, response_size, gfp);
416	if (msg) {
417		struct virtio_snd_pcm_hdr *hdr = virtsnd_ctl_msg_request(msg);
418
419		hdr->hdr.code = cpu_to_le32(command);
420		hdr->stream_id = cpu_to_le32(vss->sid);
421	}
422
423	return msg;
424}
425