sound/virtio/virtio_pcm_msg.c

   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[0];
  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(sizeof(*msg) + sizeof(*msg->sgs) * (sg_num + 2),
 150                               GFP_KERNEL);
 151                 if (!msg)
 152                         return -ENOMEM;
 153
 154                 msg->substream = vss;
 155                 sg_init_one(&msg->sgs[PCM_MSG_SG_XFER], &msg->xfer,
 156                             sizeof(msg->xfer));
 157                 sg_init_one(&msg->sgs[PCM_MSG_SG_STATUS], &msg->status,
 158                             sizeof(msg->status));
 159                 msg->length = period_bytes;
 160                 virtsnd_pcm_sg_from(&msg->sgs[PCM_MSG_SG_DATA], sg_num, data,
 161                                     period_bytes);
 162
 163                 vss->msgs[i] = msg;
 164         }
 165
 166         return 0;
 167 }
 168
 169 /**
 170  * virtsnd_pcm_msg_free() - Free all allocated I/O messages.
 171  * @vss: VirtIO PCM substream.
 172  *
 173  * Context: Any context.
 174  */
 175 void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss)
 176 {
 177         unsigned int i;
 178
 179         for (i = 0; vss->msgs && i < vss->nmsgs; ++i)
 180                 kfree(vss->msgs[i]);
 181         kfree(vss->msgs);
 182
 183         vss->msgs = NULL;
 184         vss->nmsgs = 0;
 185 }
 186
 187 /**
 188  * virtsnd_pcm_msg_send() - Send asynchronous I/O messages.
 189  * @vss: VirtIO PCM substream.
 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 keeps track of two values:
 194  *
 195  *   msg_last_enqueued = index of the last enqueued message,
 196  *   msg_count = # of pending messages in the virtqueue.
 197  *
 198  * Context: Any context. Expects the tx/rx queue and the VirtIO substream
 199  *          spinlocks to be held by caller.
 200  * Return: 0 on success, -errno on failure.
 201  */
 202 int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss)
 203 {
 204         struct snd_pcm_runtime *runtime = vss->substream->runtime;
 205         struct virtio_snd *snd = vss->snd;
 206         struct virtio_device *vdev = snd->vdev;
 207         struct virtqueue *vqueue = virtsnd_pcm_queue(vss)->vqueue;
 208         int i;
 209         int n;
 210         bool notify = false;
 211
 212         i = (vss->msg_last_enqueued + 1) % runtime->periods;
 213         n = runtime->periods - vss->msg_count;
 214
 215         for (; n; --n, i = (i + 1) % runtime->periods) {
 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                 int rc;
 223
 224                 msg->xfer.stream_id = cpu_to_le32(vss->sid);
 225                 memset(&msg->status, 0, sizeof(msg->status));
 226
 227                 if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK)
 228                         rc = virtqueue_add_sgs(vqueue, psgs, 2, 1, msg,
 229                                                GFP_ATOMIC);
 230                 else
 231                         rc = virtqueue_add_sgs(vqueue, psgs, 1, 2, msg,
 232                                                GFP_ATOMIC);
 233
 234                 if (rc) {
 235                         dev_err(&vdev->dev,
 236                                 "SID %u: failed to send I/O message\n",
 237                                 vss->sid);
 238                         return rc;
 239                 }
 240
 241                 vss->msg_last_enqueued = i;
 242                 vss->msg_count++;
 243         }
 244
 245         if (!(vss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING)))
 246                 notify = virtqueue_kick_prepare(vqueue);
 247
 248         if (notify)
 249                 virtqueue_notify(vqueue);
 250
 251         return 0;
 252 }
 253
 254 /**
 255  * virtsnd_pcm_msg_pending_num() - Returns the number of pending I/O messages.
 256  * @vss: VirtIO substream.
 257  *
 258  * Context: Any context.
 259  * Return: Number of messages.
 260  */
 261 unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss)
 262 {
 263         unsigned int num;
 264         unsigned long flags;
 265
 266         spin_lock_irqsave(&vss->lock, flags);
 267         num = vss->msg_count;
 268         spin_unlock_irqrestore(&vss->lock, flags);
 269
 270         return num;
 271 }
 272
 273 /**
 274  * virtsnd_pcm_msg_complete() - Complete an I/O message.
 275  * @msg: I/O message.
 276  * @written_bytes: Number of bytes written to the message.
 277  *
 278  * Completion of the message means the elapsed period. If transmission is
 279  * allowed, then each completed message is immediately placed back at the end
 280  * of the queue.
 281  *
 282  * For the playback substream, @written_bytes is equal to sizeof(msg->status).
 283  *
 284  * For the capture substream, @written_bytes is equal to sizeof(msg->status)
 285  * plus the number of captured bytes.
 286  *
 287  * Context: Interrupt context. Takes and releases the VirtIO substream spinlock.
 288  */
 289 static void virtsnd_pcm_msg_complete(struct virtio_pcm_msg *msg,
 290                                      size_t written_bytes)
 291 {
 292         struct virtio_pcm_substream *vss = msg->substream;
 293
 294         /*
 295          * hw_ptr always indicates the buffer position of the first I/O message
 296          * in the virtqueue. Therefore, on each completion of an I/O message,
 297          * the hw_ptr value is unconditionally advanced.
 298          */
 299         spin_lock(&vss->lock);
 300         /*
 301          * If the capture substream returned an incorrect status, then just
 302          * increase the hw_ptr by the message size.
 303          */
 304         if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK ||
 305             written_bytes <= sizeof(msg->status))
 306                 vss->hw_ptr += msg->length;
 307         else
 308                 vss->hw_ptr += written_bytes - sizeof(msg->status);
 309
 310         if (vss->hw_ptr >= vss->buffer_bytes)
 311                 vss->hw_ptr -= vss->buffer_bytes;
 312
 313         vss->xfer_xrun = false;
 314         vss->msg_count--;
 315
 316         if (vss->xfer_enabled) {
 317                 struct snd_pcm_runtime *runtime = vss->substream->runtime;
 318
 319                 runtime->delay =
 320                         bytes_to_frames(runtime,
 321                                         le32_to_cpu(msg->status.latency_bytes));
 322
 323                 schedule_work(&vss->elapsed_period);
 324
 325                 virtsnd_pcm_msg_send(vss);
 326         } else if (!vss->msg_count) {
 327                 wake_up_all(&vss->msg_empty);
 328         }
 329         spin_unlock(&vss->lock);
 330 }
 331
 332 /**
 333  * virtsnd_pcm_notify_cb() - Process all completed I/O messages.
 334  * @queue: Underlying tx/rx virtqueue.
 335  *
 336  * Context: Interrupt context. Takes and releases the tx/rx queue spinlock.
 337  */
 338 static inline void virtsnd_pcm_notify_cb(struct virtio_snd_queue *queue)
 339 {
 340         struct virtio_pcm_msg *msg;
 341         u32 written_bytes;
 342         unsigned long flags;
 343
 344         spin_lock_irqsave(&queue->lock, flags);
 345         do {
 346                 virtqueue_disable_cb(queue->vqueue);
 347                 while ((msg = virtqueue_get_buf(queue->vqueue, &written_bytes)))
 348                         virtsnd_pcm_msg_complete(msg, written_bytes);
 349                 if (unlikely(virtqueue_is_broken(queue->vqueue)))
 350                         break;
 351         } while (!virtqueue_enable_cb(queue->vqueue));
 352         spin_unlock_irqrestore(&queue->lock, flags);
 353 }
 354
 355 /**
 356  * virtsnd_pcm_tx_notify_cb() - Process all completed TX messages.
 357  * @vqueue: Underlying tx virtqueue.
 358  *
 359  * Context: Interrupt context.
 360  */
 361 void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue)
 362 {
 363         struct virtio_snd *snd = vqueue->vdev->priv;
 364
 365         virtsnd_pcm_notify_cb(virtsnd_tx_queue(snd));
 366 }
 367
 368 /**
 369  * virtsnd_pcm_rx_notify_cb() - Process all completed RX messages.
 370  * @vqueue: Underlying rx virtqueue.
 371  *
 372  * Context: Interrupt context.
 373  */
 374 void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue)
 375 {
 376         struct virtio_snd *snd = vqueue->vdev->priv;
 377
 378         virtsnd_pcm_notify_cb(virtsnd_rx_queue(snd));
 379 }
 380
 381 /**
 382  * virtsnd_pcm_ctl_msg_alloc() - Allocate and initialize the PCM device control
 383  *                               message for the specified substream.
 384  * @vss: VirtIO PCM substream.
 385  * @command: Control request code (VIRTIO_SND_R_PCM_XXX).
 386  * @gfp: Kernel flags for memory allocation.
 387  *
 388  * Context: Any context. May sleep if @gfp flags permit.
 389  * Return: Allocated message on success, NULL on failure.
 390  */
 391 struct virtio_snd_msg *
 392 virtsnd_pcm_ctl_msg_alloc(struct virtio_pcm_substream *vss,
 393                           unsigned int command, gfp_t gfp)
 394 {
 395         size_t request_size = sizeof(struct virtio_snd_pcm_hdr);
 396         size_t response_size = sizeof(struct virtio_snd_hdr);
 397         struct virtio_snd_msg *msg;
 398
 399         switch (command) {
 400         case VIRTIO_SND_R_PCM_SET_PARAMS:
 401                 request_size = sizeof(struct virtio_snd_pcm_set_params);
 402                 break;
 403         }
 404
 405         msg = virtsnd_ctl_msg_alloc(request_size, response_size, gfp);
 406         if (msg) {
 407                 struct virtio_snd_pcm_hdr *hdr = virtsnd_ctl_msg_request(msg);
 408
 409                 hdr->hdr.code = cpu_to_le32(command);
 410                 hdr->stream_id = cpu_to_le32(vss->sid);
 411         }
 412
 413         return msg;
 414 }