[ALSA] Use posix clock monotonic for PCM and timer timestamps

We need an accurate and continuous (monotonic) time sources to do
accurate synchronization among more timing sources. This patch allows
to enable monotonic timestamps for ALSA PCM devices and enables monotonic
timestamps for ALSA timer devices.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

2 files changed, 18 insertions, 2 deletions

diff --git a/include/sound/asound.h b/include/sound/asound.h
index 3ad534149c06..475eb71d65ba 100644
--- a/include/sound/asound.h
+++ b/include/sound/asound.h
@@ -138,7 +138,7 @@ enum {
  *                                                                           *
  *****************************************************************************/
 
-#define SNDRV_PCM_VERSION               SNDRV_PROTOCOL_VERSION(2, 0, 8)
+#define SNDRV_PCM_VERSION               SNDRV_PROTOCOL_VERSION(2, 0, 9)
 
 typedef unsigned long snd_pcm_uframes_t;
 typedef signed long snd_pcm_sframes_t;
@@ -435,9 +435,15 @@ struct snd_xfern {
 };
 
 enum {
+        SNDRV_PCM_TSTAMP_TYPE_GETTIMEOFDAY = 0, /* gettimeofday equivalent */
+        SNDRV_PCM_TSTAMP_TYPE_MONOTONIC,        /* posix_clock_monotonic equivalent */
+        SNDRV_PCM_TSTAMP_TYPE_LAST = SNDRV_PCM_TSTAMP_TYPE_MONOTONIC,
+};
+
+enum {
         SNDRV_PCM_IOCTL_PVERSION = _IOR('A', 0x00, int),
         SNDRV_PCM_IOCTL_INFO = _IOR('A', 0x01, struct snd_pcm_info),
-        SNDRV_PCM_IOCTL_TSTAMP = _IOW('A', 0x02, int),
+        SNDRV_PCM_IOCTL_TTSTAMP = _IOW('A', 0x03, int),
         SNDRV_PCM_IOCTL_HW_REFINE = _IOWR('A', 0x10, struct snd_pcm_hw_params),
         SNDRV_PCM_IOCTL_HW_PARAMS = _IOWR('A', 0x11, struct snd_pcm_hw_params),
         SNDRV_PCM_IOCTL_HW_FREE = _IO('A', 0x12),
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 5e9cc460075e..65f636223d39 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -323,6 +323,7 @@ struct snd_pcm_runtime {
 
         /* -- timer -- */
         unsigned int timer_resolution;  /* timer resolution */
+        int tstamp_type;                /* timestamp type */
 
         /* -- DMA -- */           
         unsigned char *dma_area;        /* DMA area */
@@ -952,6 +953,15 @@ void snd_pcm_timer_resolution_change(struct snd_pcm_substream *substream);
 void snd_pcm_timer_init(struct snd_pcm_substream *substream);
 void snd_pcm_timer_done(struct snd_pcm_substream *substream);
 
+static inline void snd_pcm_gettime(struct snd_pcm_runtime *runtime,
+                                   struct timespec *tv)
+{
+        if (runtime->tstamp_type == SNDRV_PCM_TSTAMP_TYPE_MONOTONIC)
+                do_posix_clock_monotonic_gettime(tv);
+        else
+                getnstimeofday(tv);
+}
+
 /*
  *  Memory
  */