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[];
  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                 msg->length = period_bytes;
 159                 virtsnd_pcm_sg_from(&msg->sgs[PCM_MSG_SG_DATA], sg_num, data,
 160                                     period_bytes);
 161
 162                 vss->msgs[i] = msg;
 163         }
 164
 165         return 0;
 166 }
 167
 168 /**
 169  * virtsnd_pcm_msg_free() - Free all allocated I/O messages.
 170  * @vss: VirtIO PCM substream.
 171  *
 172  * Context: Any context.
 173  */
 174 void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss)
 175 {
 176         unsigned int i;
 177
 178         for (i = 0; vss->msgs && i < vss->nmsgs; ++i)
 179                 kfree(vss->msgs[i]);
 180         kfree(vss->msgs);
 181
 182         vss->msgs = NULL;
 183         vss->nmsgs = 0;
 184 }
 185
 186 /**
 187  * virtsnd_pcm_msg_send() - Send asynchronous I/O messages.
 188  * @vss: VirtIO PCM substream.
 189  *
 190  * All messages are organized in an ordered circular list. Each time the
 191  * function is called, all currently non-enqueued messages are added to the
 192  * virtqueue. For this, the function keeps track of two values:
 193  *
 194  *   msg_last_enqueued = index of the last enqueued message,
 195  *   msg_count = # of pending messages in the virtqueue.
 196  *
 197  * Context: Any context. Expects the tx/rx queue and the VirtIO substream
 198  *          spinlocks to be held by caller.
 199  * Return: 0 on success, -errno on failure.
 200  */
 201 int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss)
 202 {
 203         struct snd_pcm_runtime *runtime = vss->substream->runtime;
 204         struct virtio_snd *snd = vss->snd;
 205         struct virtio_device *vdev = snd->vdev;
 206         struct virtqueue *vqueue = virtsnd_pcm_queue(vss)->vqueue;
 207         int i;
 208         int n;
 209         bool notify = false;
 210
 211         i = (vss->msg_last_enqueued + 1) % runtime->periods;
 212         n = runtime->periods - vss->msg_count;
 213
 214         for (; n; --n, i = (i + 1) % runtime->periods) {
 215                 struct virtio_pcm_msg *msg = vss->msgs[i];
 216                 struct scatterlist *psgs[] = {
 217                         &msg->sgs[PCM_MSG_SG_XFER],
 218                         &msg->sgs[PCM_MSG_SG_DATA],
 219                         &msg->sgs[PCM_MSG_SG_STATUS]
 220                 };
 221                 int rc;
 222
 223                 msg->xfer.stream_id = cpu_to_le32(vss->sid);
 224                 memset(&msg->status, 0, sizeof(msg->status));
 225
 226                 if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK)
 227                         rc = virtqueue_add_sgs(vqueue, psgs, 2, 1, msg,
 228                                                GFP_ATOMIC);
 229                 else
 230                         rc = virtqueue_add_sgs(vqueue, psgs, 1, 2, msg,
 231                                                GFP_ATOMIC);
 232
 233                 if (rc) {
 234                         dev_err(&vdev->dev,
 235                                 "SID %u: failed to send I/O message\n",
 236                                 vss->sid);
 237                         return rc;
 238                 }
 239
 240                 vss->msg_last_enqueued = i;
 241                 vss->msg_count++;
 242         }
 243
 244         if (!(vss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING)))
 245                 notify = virtqueue_kick_prepare(vqueue);
 246
 247         if (notify)
 248                 virtqueue_notify(vqueue);
 249
 250         return 0;
 251 }
 252
 253 /**
 254  * virtsnd_pcm_msg_pending_num() - Returns the number of pending I/O messages.
 255  * @vss: VirtIO substream.
 256  *
 257  * Context: Any context.
 258  * Return: Number of messages.
 259  */
 260 unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss)
 261 {
 262         unsigned int num;
 263         unsigned long flags;
 264
 265         spin_lock_irqsave(&vss->lock, flags);
 266         num = vss->msg_count;
 267         spin_unlock_irqrestore(&vss->lock, flags);
 268
 269         return num;
 270 }
 271
 272 /**
 273  * virtsnd_pcm_msg_complete() - Complete an I/O message.
 274  * @msg: I/O message.
 275  * @written_bytes: Number of bytes written to the message.
 276  *
 277  * Completion of the message means the elapsed period. If transmission is
 278  * allowed, then each completed message is immediately placed back at the end
 279  * of the queue.
 280  *
 281  * For the playback substream, @written_bytes is equal to sizeof(msg->status).
 282  *
 283  * For the capture substream, @written_bytes is equal to sizeof(msg->status)
 284  * plus the number of captured bytes.
 285  *
 286  * Context: Interrupt context. Takes and releases the VirtIO substream spinlock.
 287  */
 288 static void virtsnd_pcm_msg_complete(struct virtio_pcm_msg *msg,
 289                                      size_t written_bytes)
 290 {
 291         struct virtio_pcm_substream *vss = msg->substream;
 292
 293         /*
 294          * hw_ptr always indicates the buffer position of the first I/O message
 295          * in the virtqueue. Therefore, on each completion of an I/O message,
 296          * the hw_ptr value is unconditionally advanced.
 297          */
 298         spin_lock(&vss->lock);
 299         /*
 300          * If the capture substream returned an incorrect status, then just
 301          * increase the hw_ptr by the message size.
 302          */
 303         if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK ||
 304             written_bytes <= sizeof(msg->status))
 305                 vss->hw_ptr += msg->length;
 306         else
 307                 vss->hw_ptr += written_bytes - sizeof(msg->status);
 308
 309         if (vss->hw_ptr >= vss->buffer_bytes)
 310                 vss->hw_ptr -= vss->buffer_bytes;
 311
 312         vss->xfer_xrun = false;
 313         vss->msg_count--;
 314
 315         if (vss->xfer_enabled) {
 316                 struct snd_pcm_runtime *runtime = vss->substream->runtime;
 317
 318                 runtime->delay =
 319                         bytes_to_frames(runtime,
 320                                         le32_to_cpu(msg->status.latency_bytes));
 321
 322                 schedule_work(&vss->elapsed_period);
 323
 324                 virtsnd_pcm_msg_send(vss);
 325         } else if (!vss->msg_count) {
 326                 wake_up_all(&vss->msg_empty);
 327         }
 328         spin_unlock(&vss->lock);
 329 }
 330
 331 /**
 332  * virtsnd_pcm_notify_cb() - Process all completed I/O messages.
 333  * @queue: Underlying tx/rx virtqueue.
 334  *
 335  * Context: Interrupt context. Takes and releases the tx/rx queue spinlock.
 336  */
 337 static inline void virtsnd_pcm_notify_cb(struct virtio_snd_queue *queue)
 338 {
 339         struct virtio_pcm_msg *msg;
 340         u32 written_bytes;
 341         unsigned long flags;
 342
 343         spin_lock_irqsave(&queue->lock, flags);
 344         do {
 345                 virtqueue_disable_cb(queue->vqueue);
 346                 while ((msg = virtqueue_get_buf(queue->vqueue, &written_bytes)))
 347                         virtsnd_pcm_msg_complete(msg, written_bytes);
 348                 if (unlikely(virtqueue_is_broken(queue->vqueue)))
 349                         break;
 350         } while (!virtqueue_enable_cb(queue->vqueue));
 351         spin_unlock_irqrestore(&queue->lock, flags);
 352 }
 353
 354 /**
 355  * virtsnd_pcm_tx_notify_cb() - Process all completed TX messages.
 356  * @vqueue: Underlying tx virtqueue.
 357  *
 358  * Context: Interrupt context.
 359  */
 360 void virtsnd_pcm_tx_notify_cb(struct virtqueue *vqueue)
 361 {
 362         struct virtio_snd *snd = vqueue->vdev->priv;
 363
 364         virtsnd_pcm_notify_cb(virtsnd_tx_queue(snd));
 365 }
 366
 367 /**
 368  * virtsnd_pcm_rx_notify_cb() - Process all completed RX messages.
 369  * @vqueue: Underlying rx virtqueue.
 370  *
 371  * Context: Interrupt context.
 372  */
 373 void virtsnd_pcm_rx_notify_cb(struct virtqueue *vqueue)
 374 {
 375         struct virtio_snd *snd = vqueue->vdev->priv;
 376
 377         virtsnd_pcm_notify_cb(virtsnd_rx_queue(snd));
 378 }
 379
 380 /**
 381  * virtsnd_pcm_ctl_msg_alloc() - Allocate and initialize the PCM device control
 382  *                               message for the specified substream.
 383  * @vss: VirtIO PCM substream.
 384  * @command: Control request code (VIRTIO_SND_R_PCM_XXX).
 385  * @gfp: Kernel flags for memory allocation.
 386  *
 387  * Context: Any context. May sleep if @gfp flags permit.
 388  * Return: Allocated message on success, NULL on failure.
 389  */
 390 struct virtio_snd_msg *
 391 virtsnd_pcm_ctl_msg_alloc(struct virtio_pcm_substream *vss,
 392                           unsigned int command, gfp_t gfp)
 393 {
 394         size_t request_size = sizeof(struct virtio_snd_pcm_hdr);
 395         size_t response_size = sizeof(struct virtio_snd_hdr);
 396         struct virtio_snd_msg *msg;
 397
 398         switch (command) {
 399         case VIRTIO_SND_R_PCM_SET_PARAMS:
 400                 request_size = sizeof(struct virtio_snd_pcm_set_params);
 401                 break;
 402         }
 403
 404         msg = virtsnd_ctl_msg_alloc(request_size, response_size, gfp);
 405         if (msg) {
 406                 struct virtio_snd_pcm_hdr *hdr = virtsnd_ctl_msg_request(msg);
 407
 408                 hdr->hdr.code = cpu_to_le32(command);
 409                 hdr->stream_id = cpu_to_le32(vss->sid);
 410         }
 411
 412         return msg;
 413 }