+/* call in cable->lock */
+static int loopback_snd_timer_check_resolution(struct snd_pcm_runtime *runtime,
+ unsigned long resolution)
+{
+ if (resolution != runtime->timer_resolution) {
+ struct loopback_pcm *dpcm = runtime->private_data;
+ struct loopback_cable *cable = dpcm->cable;
+ /* Worst case estimation of possible values for resolution
+ * resolution <= (512 * 1024) frames / 8kHz in nsec
+ * resolution <= 65.536.000.000 nsec
+ *
+ * period_size <= 65.536.000.000 nsec / 1000nsec/usec * 192kHz +
+ * 500.000
+ * period_size <= 12.582.912.000.000 <64bit
+ * / 1.000.000 usec/sec
+ */
+ snd_pcm_uframes_t period_size_usec =
+ resolution / 1000 * runtime->rate;
+ /* round to nearest sample rate */
+ snd_pcm_uframes_t period_size =
+ (period_size_usec + 500 * 1000) / (1000 * 1000);
+
+ pcm_err(dpcm->substream->pcm,
+ "Period size (%lu frames) of loopback device is not corresponding to timer resolution (%lu nsec = %lu frames) of card timer %d,%d,%d. Use period size of %lu frames for loopback device.",
+ runtime->period_size, resolution, period_size,
+ cable->snd_timer.id.card,
+ cable->snd_timer.id.device,
+ cable->snd_timer.id.subdevice,
+ period_size);
+ return -EINVAL;
+ }
+ return 0;
+}
+
+static void loopback_snd_timer_period_elapsed(struct loopback_cable *cable,
+ int event,
+ unsigned long resolution)
+{
+ struct loopback_pcm *dpcm_play, *dpcm_capt;
+ struct snd_pcm_substream *substream_play, *substream_capt;
+ struct snd_pcm_runtime *valid_runtime;
+ unsigned int running, elapsed_bytes;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cable->lock, flags);
+ running = cable->running ^ cable->pause;
+ /* no need to do anything if no stream is running */
+ if (!running) {
+ spin_unlock_irqrestore(&cable->lock, flags);
+ return;
+ }
+
+ dpcm_play = cable->streams[SNDRV_PCM_STREAM_PLAYBACK];
+ dpcm_capt = cable->streams[SNDRV_PCM_STREAM_CAPTURE];
+ substream_play = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ?
+ dpcm_play->substream : NULL;
+ substream_capt = (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) ?
+ dpcm_capt->substream : NULL;
+
+ if (event == SNDRV_TIMER_EVENT_MSTOP) {
+ if (!dpcm_play ||
+ dpcm_play->substream->runtime->status->state !=
+ SNDRV_PCM_STATE_DRAINING) {
+ spin_unlock_irqrestore(&cable->lock, flags);
+ return;
+ }
+ }
+
+ valid_runtime = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ?
+ dpcm_play->substream->runtime :
+ dpcm_capt->substream->runtime;
+
+ /* resolution is only valid for SNDRV_TIMER_EVENT_TICK events */
+ if (event == SNDRV_TIMER_EVENT_TICK) {
+ /* The hardware rules guarantee that playback and capture period
+ * are the same. Therefore only one device has to be checked
+ * here.
+ */
+ if (loopback_snd_timer_check_resolution(valid_runtime,
+ resolution) < 0) {
+ spin_unlock_irqrestore(&cable->lock, flags);
+ if (substream_play)
+ snd_pcm_stop_xrun(substream_play);
+ if (substream_capt)
+ snd_pcm_stop_xrun(substream_capt);
+ return;
+ }
+ }
+
+ elapsed_bytes = frames_to_bytes(valid_runtime,
+ valid_runtime->period_size);
+ /* The same timer interrupt is used for playback and capture device */
+ if ((running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) &&
+ (running & (1 << SNDRV_PCM_STREAM_CAPTURE))) {
+ copy_play_buf(dpcm_play, dpcm_capt, elapsed_bytes);
+ bytepos_finish(dpcm_play, elapsed_bytes);
+ bytepos_finish(dpcm_capt, elapsed_bytes);
+ } else if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
+ bytepos_finish(dpcm_play, elapsed_bytes);
+ } else if (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) {
+ clear_capture_buf(dpcm_capt, elapsed_bytes);
+ bytepos_finish(dpcm_capt, elapsed_bytes);
+ }
+ spin_unlock_irqrestore(&cable->lock, flags);
+
+ if (substream_play)
+ snd_pcm_period_elapsed(substream_play);
+ if (substream_capt)
+ snd_pcm_period_elapsed(substream_capt);
+}
+
+static void loopback_snd_timer_function(struct snd_timer_instance *timeri,
+ unsigned long resolution,
+ unsigned long ticks)
+{
+ struct loopback_cable *cable = timeri->callback_data;
+
+ loopback_snd_timer_period_elapsed(cable, SNDRV_TIMER_EVENT_TICK,
+ resolution);
+}
+
+static void loopback_snd_timer_tasklet(unsigned long arg)
+{
+ struct snd_timer_instance *timeri = (struct snd_timer_instance *)arg;
+ struct loopback_cable *cable = timeri->callback_data;
+
+ loopback_snd_timer_period_elapsed(cable, SNDRV_TIMER_EVENT_MSTOP, 0);
+}
+
+static void loopback_snd_timer_event(struct snd_timer_instance *timeri,
+ int event,
+ struct timespec *tstamp,
+ unsigned long resolution)
+{
+ /* Do not lock cable->lock here because timer->lock is already hold.
+ * There are other functions which first lock cable->lock and than
+ * timer->lock e.g.
+ * loopback_trigger()
+ * spin_lock(&cable->lock)
+ * loopback_snd_timer_start()
+ * snd_timer_start()
+ * spin_lock(&timer->lock)
+ * Therefore when using the oposit order of locks here it could result
+ * in a deadlock.
+ */
+
+ if (event == SNDRV_TIMER_EVENT_MSTOP) {
+ struct loopback_cable *cable = timeri->callback_data;
+
+ /* sound card of the timer was stopped. Therefore there will not
+ * be any further timer callbacks. Due to this forward audio
+ * data from here if in draining state. When still in running
+ * state the streaming will be aborted by the usual timeout. It
+ * should not be aborted here because may be the timer sound
+ * card does only a recovery and the timer is back soon.
+ * This tasklet triggers loopback_snd_timer_tasklet()
+ */
+ tasklet_schedule(&cable->snd_timer.event_tasklet);
+ }
+}
+