ALSA: core: selection of audio_tstamp type and accuracy reports

Audio timestamps can be extracted from sample counters, wall clocks,
PHC clocks (Ethernet AVB), on-demand synchronized snapshots. This
patch provides the ability to report timestamping capabilities, select
timestamp types and retrieve timestamp accuracy, if supported.
Details can be found in Documentations/sound/alsa/timestamping.txt

This functionality is introduced by reclaiming the reserved_aligned
field introduced by commit9c7066aef4a5eb8e4063de28f06c508bf6f2963a
in snd_pcm_status to provide userspace with selection/query capabilities.
Additional driver_tstamp and audio_tstamp_accuracy fields are also added.

snd_pcm_mmap_status remains a read-only structure with only
the audio timestamp value accessible from user space. The selection
of audio timestamp type is done through snd_pcm_status only

This commit does not impact ABI and does not impact the default
behavior. By default audio timestamp is aligned with hw_pointer and
reports the DMA position. Backwards compatibility is handled by using
the HDAudio wall clock for playback and the hw_ptr for all other
cases.

For timestamp selection a new STATUS_EXT ioctl is introduced with
read/write parameters. Alsa-lib will be modified to make use of
STATUS_EXT.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 30 insertions, 4 deletions

diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 0e88e7a0f0eb..acef4e4d2735 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -267,10 +267,17 @@ typedef int __bitwise snd_pcm_subformat_t;
 #define SNDRV_PCM_INFO_JOINT_DUPLEX     0x00200000      /* playback and capture stream are somewhat correlated */
 #define SNDRV_PCM_INFO_SYNC_START       0x00400000      /* pcm support some kind of sync go */
 #define SNDRV_PCM_INFO_NO_PERIOD_WAKEUP 0x00800000      /* period wakeup can be disabled */
-#define SNDRV_PCM_INFO_HAS_WALL_CLOCK   0x01000000      /* has audio wall clock for audio/system time sync */
+#define SNDRV_PCM_INFO_HAS_WALL_CLOCK   0x01000000      /* (Deprecated)has audio wall clock for audio/system time sync */
+#define SNDRV_PCM_INFO_HAS_LINK_ATIME              0x01000000  /* report hardware link audio time, reset on startup */
+#define SNDRV_PCM_INFO_HAS_LINK_ABSOLUTE_ATIME     0x02000000  /* report absolute hardware link audio time, not reset on startup */
+#define SNDRV_PCM_INFO_HAS_LINK_ESTIMATED_ATIME    0x04000000  /* report estimated link audio time */
+#define SNDRV_PCM_INFO_HAS_LINK_SYNCHRONIZED_ATIME 0x08000000  /* report synchronized audio/system time */
+
 #define SNDRV_PCM_INFO_DRAIN_TRIGGER    0x40000000              /* internal kernel flag - trigger in drain */
 #define SNDRV_PCM_INFO_FIFO_IN_FRAMES   0x80000000      /* internal kernel flag - FIFO size is in frames */
 
+
+
 typedef int __bitwise snd_pcm_state_t;
 #define SNDRV_PCM_STATE_OPEN            ((__force snd_pcm_state_t) 0) /* stream is open */
 #define SNDRV_PCM_STATE_SETUP           ((__force snd_pcm_state_t) 1) /* stream has a setup */
@@ -408,6 +415,22 @@ struct snd_pcm_channel_info {
         unsigned int step;              /* samples distance in bits */
 };
 
+enum {
+        /*
+         *  first definition for backwards compatibility only,
+         *  maps to wallclock/link time for HDAudio playback and DEFAULT/DMA time for everything else
+         */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_COMPAT = 0,
+
+        /* timestamp definitions */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT = 1,           /* DMA time, reported as per hw_ptr */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_LINK = 2,              /* link time reported by sample or wallclock counter, reset on startup */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_LINK_ABSOLUTE = 3,     /* link time reported by sample or wallclock counter, not reset on startup */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_LINK_ESTIMATED = 4,    /* link time estimated indirectly */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_LINK_SYNCHRONIZED = 5, /* link time synchronized with system time */
+        SNDRV_PCM_AUDIO_TSTAMP_TYPE_LAST = SNDRV_PCM_AUDIO_TSTAMP_TYPE_LINK_SYNCHRONIZED
+};
+
 struct snd_pcm_status {
         snd_pcm_state_t state;          /* stream state */
         struct timespec trigger_tstamp; /* time when stream was started/stopped/paused */
@@ -419,9 +442,11 @@ struct snd_pcm_status {
         snd_pcm_uframes_t avail_max;    /* max frames available on hw since last status */
         snd_pcm_uframes_t overrange;    /* count of ADC (capture) overrange detections from last status */
         snd_pcm_state_t suspended_state; /* suspended stream state */
-        __u32 reserved_alignment;       /* must be filled with zero */
-        struct timespec audio_tstamp;   /* from sample counter or wall clock */
-        unsigned char reserved[56-sizeof(struct timespec)]; /* must be filled with zero */
+        __u32 audio_tstamp_data;         /* needed for 64-bit alignment, used for configs/report to/from userspace */
+        struct timespec audio_tstamp;   /* sample counter, wall clock, PHC or on-demand sync'ed */
+        struct timespec driver_tstamp;  /* useful in case reference system tstamp is reported with delay */
+        __u32 audio_tstamp_accuracy;    /* in ns units, only valid if indicated in audio_tstamp_data */
+        unsigned char reserved[52-2*sizeof(struct timespec)]; /* must be filled with zero */
 };
 
 struct snd_pcm_mmap_status {
@@ -534,6 +559,7 @@ enum {
 #define SNDRV_PCM_IOCTL_DELAY           _IOR('A', 0x21, snd_pcm_sframes_t)
 #define SNDRV_PCM_IOCTL_HWSYNC          _IO('A', 0x22)
 #define SNDRV_PCM_IOCTL_SYNC_PTR        _IOWR('A', 0x23, struct snd_pcm_sync_ptr)
+#define SNDRV_PCM_IOCTL_STATUS_EXT      _IOWR('A', 0x24, struct snd_pcm_status)
 #define SNDRV_PCM_IOCTL_CHANNEL_INFO    _IOR('A', 0x32, struct snd_pcm_channel_info)
 #define SNDRV_PCM_IOCTL_PREPARE         _IO('A', 0x40)
 #define SNDRV_PCM_IOCTL_RESET           _IO('A', 0x41)