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

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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>
This commit is contained in:
Jaroslav Kysela
2007-12-13 10:19:42 +01:00
parent 25543fa785
commit b751eef1fd
5 changed files with 52 additions and 11 deletions
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16
sound/core/timer.c
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@ -44,11 +44,14 @@
#endif
static int timer_limit = DEFAULT_TIMER_LIMIT;
static int timer_tstamp_monotonic = 1;
MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.de>");
MODULE_DESCRIPTION("ALSA timer interface");
MODULE_LICENSE("GPL");
module_param(timer_limit, int, 0444);
MODULE_PARM_DESC(timer_limit, "Maximum global timers in system.");
module_param(timer_tstamp_monotonic, int, 0444);
MODULE_PARM_DESC(timer_tstamp_monotonic, "Use posix monotonic clock source for timestamps (default).");
struct snd_timer_user {
struct snd_timer_instance *timeri;
@ -381,7 +384,10 @@ static void snd_timer_notify1(struct snd_timer_instance *ti, int event)
struct snd_timer_instance *ts;
struct timespec tstamp;
getnstimeofday(&tstamp);
if (timer_tstamp_monotonic)
do_posix_clock_monotonic_gettime(&tstamp);
else
getnstimeofday(&tstamp);
snd_assert(event >= SNDRV_TIMER_EVENT_START &&
event <= SNDRV_TIMER_EVENT_PAUSE, return);
if (event == SNDRV_TIMER_EVENT_START ||
@ -1182,8 +1188,12 @@ static void snd_timer_user_tinterrupt(struct snd_timer_instance *timeri,
spin_unlock(&tu->qlock);
return;
}
if (tu->last_resolution != resolution || ticks > 0)
getnstimeofday(&tstamp);
if (tu->last_resolution != resolution || ticks > 0) {
if (timer_tstamp_monotonic)
do_posix_clock_monotonic_gettime(&tstamp);
else
getnstimeofday(&tstamp);
}
if ((tu->filter & (1 << SNDRV_TIMER_EVENT_RESOLUTION)) &&
tu->last_resolution != resolution) {
r1.event = SNDRV_TIMER_EVENT_RESOLUTION;