xref: /linux/sound/virtio/virtio_pcm_msg.c (revision 906fd46a65383cd639e5eec72a047efc33045d86)
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  */
18 struct 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  */
33 enum 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  */
48 static 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  */
90 static 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  */
132 int 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  */
173 void 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  */
200 int 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  */
273 unsigned 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  */
301 static 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  */
350 static 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  */
371 void 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  */
384 void 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  */
401 struct virtio_snd_msg *
402 virtsnd_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