From 826c8f69d34ef49e86fe0ab6c93c1ffba8916131 Mon Sep 17 00:00:00 2001 From: Lars-Peter Clausen Date: Sat, 30 Nov 2013 18:07:24 +0100 Subject: [PATCH] alsa: Disable timer-scheduling for PCMs with the BATCH flag PCM Devices which have the BATCH flag set update the PCM pointer only with period size granularity. Using timer based scheduling does not have any advantage in this mode. For one devices which have that flag set usually update the position pointer in software after getting the period interrupt. So disabling the period interrupt is not possible for this kind of devices. Furthermore writing to or reading from the buffer slice for the current period is not possible since the position inside the buffer is not known. On the other hand the tsched algorithm seems to get easily confused for this kind of hardware, which results in garbled audio output. This typically means that timer based scheduling needs to be manually disabled on systems with such devices. Auto disabling tsched in this case allows these systems to run with the default configuration. Signed-off-by: Lars-Peter Clausen --- src/modules/alsa/alsa-util.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c index 75f5858..4b24e47 100644 --- a/src/modules/alsa/alsa-util.c +++ b/src/modules/alsa/alsa-util.c @@ -245,6 +245,10 @@ int pa_alsa_set_hw_params( if (!pa_alsa_pcm_is_hw(pcm_handle)) _use_tsched = false; + /* The PCM pointer is only updated with period granularity */ + if (snd_pcm_hw_params_is_batch(hwparams)) + _use_tsched = false; + #if (SND_LIB_VERSION >= ((1<<16)|(0<<8)|24)) /* API additions in 1.0.24 */ if (_use_tsched) { -- 2.7.4