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ALSA: pcm: optimize xrun detection in no-period-wakeup mode

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Add a lightweight condition on top of the xrun checking so that we can
avoid the division when the application is calling the update function
often enough.

Suggested-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Clemens Ladisch 2010-11-18 09:53:07 +01:00 committed by Takashi Iwai
parent 59ff878ffb
commit 47228e48ae
1 changed files with 2 additions and 0 deletions
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sound/core/pcm_lib.c
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@ -380,6 +380,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
* the elapsed time to detect xruns.
*/
jdelta = jiffies - runtime->hw_ptr_jiffies;
if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
goto no_delta_check;
hdelta = jdelta - delta * HZ / runtime->rate;
while (hdelta > runtime->hw_ptr_buffer_jiffies / 2 + 1) {
delta += runtime->buffer_size;