ALSA: core: add hooks for audio timestamps
ALSA did not provide any direct means to infer the audio time for A/V sync and system/audio time correlations (eg. PulseAudio). Applications had to track the number of samples read/written and add/subtract the number of samples queued in the ring buffer. This accounting led to small errors, typically several samples, due to the two-step process. Computing the audio time in the kernel is more direct, as all the information is available in the same routines. Also add new .audio_wallclock routine to enable fine-grain synchronization between monotonic system time and audio hardware time. Using the wallclock, if supported in hardware, allows for a much better sub-microsecond precision and a common drift tracking for all devices sharing the same wall clock (master clock). Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
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@ -71,6 +71,8 @@ struct snd_pcm_ops {
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int (*prepare)(struct snd_pcm_substream *substream);
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int (*trigger)(struct snd_pcm_substream *substream, int cmd);
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snd_pcm_uframes_t (*pointer)(struct snd_pcm_substream *substream);
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int (*wall_clock)(struct snd_pcm_substream *substream,
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struct timespec *audio_ts);
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int (*copy)(struct snd_pcm_substream *substream, int channel,
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snd_pcm_uframes_t pos,
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void __user *buf, snd_pcm_uframes_t count);
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@ -136,7 +136,7 @@ struct snd_hwdep_dsp_image {
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* *
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*****************************************************************************/
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#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 10)
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#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 11)
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typedef unsigned long snd_pcm_uframes_t;
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typedef signed long snd_pcm_sframes_t;
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@ -258,6 +258,7 @@ typedef int __bitwise snd_pcm_subformat_t;
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#define SNDRV_PCM_INFO_JOINT_DUPLEX 0x00200000 /* playback and capture stream are somewhat correlated */
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#define SNDRV_PCM_INFO_SYNC_START 0x00400000 /* pcm support some kind of sync go */
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#define SNDRV_PCM_INFO_NO_PERIOD_WAKEUP 0x00800000 /* period wakeup can be disabled */
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#define SNDRV_PCM_INFO_HAS_WALL_CLOCK 0x01000000 /* has audio wall clock for audio/system time sync */
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#define SNDRV_PCM_INFO_FIFO_IN_FRAMES 0x80000000 /* internal kernel flag - FIFO size is in frames */
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typedef int __bitwise snd_pcm_state_t;
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@ -406,7 +407,8 @@ struct snd_pcm_status {
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snd_pcm_uframes_t avail_max; /* max frames available on hw since last status */
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snd_pcm_uframes_t overrange; /* count of ADC (capture) overrange detections from last status */
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snd_pcm_state_t suspended_state; /* suspended stream state */
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unsigned char reserved[60]; /* must be filled with zero */
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struct timespec audio_tstamp; /* from sample counter or wall clock */
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unsigned char reserved[60-sizeof(struct timespec)]; /* must be filled with zero */
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};
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struct snd_pcm_mmap_status {
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@ -415,6 +417,7 @@ struct snd_pcm_mmap_status {
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snd_pcm_uframes_t hw_ptr; /* RO: hw ptr (0...boundary-1) */
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struct timespec tstamp; /* Timestamp */
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snd_pcm_state_t suspended_state; /* RO: suspended stream state */
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struct timespec audio_tstamp; /* from sample counter or wall clock */
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};
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struct snd_pcm_mmap_control {
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@ -190,7 +190,8 @@ struct snd_pcm_status32 {
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u32 avail_max;
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u32 overrange;
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s32 suspended_state;
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unsigned char reserved[60];
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struct compat_timespec audio_tstamp;
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unsigned char reserved[60-sizeof(struct compat_timespec)];
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} __attribute__((packed));
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@ -205,17 +206,16 @@ static int snd_pcm_status_user_compat(struct snd_pcm_substream *substream,
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return err;
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if (put_user(status.state, &src->state) ||
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put_user(status.trigger_tstamp.tv_sec, &src->trigger_tstamp.tv_sec) ||
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put_user(status.trigger_tstamp.tv_nsec, &src->trigger_tstamp.tv_nsec) ||
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put_user(status.tstamp.tv_sec, &src->tstamp.tv_sec) ||
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put_user(status.tstamp.tv_nsec, &src->tstamp.tv_nsec) ||
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compat_put_timespec(&status.trigger_tstamp, &src->trigger_tstamp) ||
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compat_put_timespec(&status.tstamp, &src->tstamp) ||
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put_user(status.appl_ptr, &src->appl_ptr) ||
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put_user(status.hw_ptr, &src->hw_ptr) ||
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put_user(status.delay, &src->delay) ||
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put_user(status.avail, &src->avail) ||
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put_user(status.avail_max, &src->avail_max) ||
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put_user(status.overrange, &src->overrange) ||
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put_user(status.suspended_state, &src->suspended_state))
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put_user(status.suspended_state, &src->suspended_state) ||
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compat_put_timespec(&status.audio_tstamp, &src->audio_tstamp))
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return -EFAULT;
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return err;
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@ -364,6 +364,7 @@ struct snd_pcm_mmap_status32 {
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u32 hw_ptr;
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struct compat_timespec tstamp;
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s32 suspended_state;
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struct compat_timespec audio_tstamp;
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} __attribute__((packed));
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struct snd_pcm_mmap_control32 {
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@ -426,12 +427,14 @@ static int snd_pcm_ioctl_sync_ptr_compat(struct snd_pcm_substream *substream,
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sstatus.hw_ptr = status->hw_ptr % boundary;
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sstatus.tstamp = status->tstamp;
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sstatus.suspended_state = status->suspended_state;
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sstatus.audio_tstamp = status->audio_tstamp;
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snd_pcm_stream_unlock_irq(substream);
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if (put_user(sstatus.state, &src->s.status.state) ||
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put_user(sstatus.hw_ptr, &src->s.status.hw_ptr) ||
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put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp.tv_sec) ||
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put_user(sstatus.tstamp.tv_nsec, &src->s.status.tstamp.tv_nsec) ||
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compat_put_timespec(&sstatus.tstamp, &src->s.status.tstamp) ||
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put_user(sstatus.suspended_state, &src->s.status.suspended_state) ||
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compat_put_timespec(&sstatus.audio_tstamp,
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&src->s.status.audio_tstamp) ||
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put_user(scontrol.appl_ptr, &src->c.control.appl_ptr) ||
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put_user(scontrol.avail_min, &src->c.control.avail_min))
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return -EFAULT;
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@ -316,6 +316,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
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unsigned long jdelta;
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unsigned long curr_jiffies;
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struct timespec curr_tstamp;
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struct timespec audio_tstamp;
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int crossed_boundary = 0;
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old_hw_ptr = runtime->status->hw_ptr;
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@ -328,9 +329,14 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
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*/
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pos = substream->ops->pointer(substream);
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curr_jiffies = jiffies;
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if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
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if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
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snd_pcm_gettime(runtime, (struct timespec *)&curr_tstamp);
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if ((runtime->hw.info & SNDRV_PCM_INFO_HAS_WALL_CLOCK) &&
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(substream->ops->wall_clock))
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substream->ops->wall_clock(substream, &audio_tstamp);
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}
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if (pos == SNDRV_PCM_POS_XRUN) {
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xrun(substream);
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return -EPIPE;
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@ -520,9 +526,31 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
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snd_BUG_ON(crossed_boundary != 1);
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runtime->hw_ptr_wrap += runtime->boundary;
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}
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if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
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if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
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runtime->status->tstamp = curr_tstamp;
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if (!(runtime->hw.info & SNDRV_PCM_INFO_HAS_WALL_CLOCK)) {
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/*
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* no wall clock available, provide audio timestamp
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* derived from pointer position+delay
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*/
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u64 audio_frames, audio_nsecs;
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if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
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audio_frames = runtime->hw_ptr_wrap
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+ runtime->status->hw_ptr
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- runtime->delay;
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else
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audio_frames = runtime->hw_ptr_wrap
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+ runtime->status->hw_ptr
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+ runtime->delay;
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audio_nsecs = div_u64(audio_frames * 1000000000LL,
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runtime->rate);
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audio_tstamp = ns_to_timespec(audio_nsecs);
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}
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runtime->status->audio_tstamp = audio_tstamp;
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}
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return snd_pcm_update_state(substream, runtime);
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}
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@ -594,6 +594,8 @@ int snd_pcm_status(struct snd_pcm_substream *substream,
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snd_pcm_update_hw_ptr(substream);
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if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
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status->tstamp = runtime->status->tstamp;
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status->audio_tstamp =
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runtime->status->audio_tstamp;
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goto _tstamp_end;
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}
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}
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