At Thu, 12 Dec 2013 15:08:11 +0900, JongHo Kim wrote:
Hi I develop ALSA SOC Part and use the tinyalsa library on application space. We recently used pause ioctl command(SNDRV_PCM_IOCTL_PAUSE) because the music application was needed to pause and resume feature. So the music application was achieved to want pause and resume feature using the SNDRV_PCM_IOCTL_PAUSE.
but I found some problem in alsa kernel framework
The music application process on pause state wake up in 10 seconds because the wait time is set by 10 seconds in wait_for_avail function.
I realized that if the 'runtime->no_period_wakeup' parameter is true, the wait_time will be set by the MAX_SCHEDULE_TIMEOUT.
I had searched other kernel source and library source. I added the SNDRV_PCM_INFO_NO_PERIOD_WAKEUP flag at my snd_pcm_hardware structure and added the SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP flag at music application(use tinyalsa library)
Result was good! The music application perfectly works the pause and resume feature.
but I have some worries if DMA or I2S was stop on the running, I can't more see the 'write error (DMA or IRQ trouble?)' message and the music application process may be sleep eternally.
I cautiously recommend next code with a solution to the above worries.
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c old mode 100644 new mode 100755 index 41b3dfe..3284940 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1936,6 +1936,8 @@ static int wait_for_avail(struct snd_pcm_substream *substream, case SNDRV_PCM_STATE_DISCONNECTED: err = -EBADFD; goto _endloop;
case SNDRV_PCM_STATE_PAUSED:continue; } if (!tout) { snd_printd("%s write error (DMA or IRQ trouble?)\n",
I tested code. code works good! but I am concerned about the side effects please review my idea.
Through my quick glance, this looks like a correct fix. Could you submit a proper patch for merging to the upstream?
thanks,
Takashi