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authorClemens Ladisch <clemens@ladisch.de>2010-11-15 10:46:23 +0100
committerTakashi Iwai <tiwai@suse.de>2010-11-22 08:13:16 +0100
commitab69a4904b5dd4d7cd6996587ba066bca8d13838 (patch)
tree8d51c631f1bd0bb72b9b528aa065ec9c0f4d0600 /sound/core
parentd2b88e4c103f37584dc81ef8a41ca584c1ce847b (diff)
ALSA: pcm: support for period wakeup disabling
This patch allows to disable period interrupts which are not needed when the application relies on a system timer to wake-up and refill the ring buffer. The behavior of the driver is left unchanged, and interrupts are only disabled if the application requests this configuration. The behavior in case of underruns is slightly different, instead of being detected during the period interrupts the underruns are detected when the application calls snd_pcm_update_avail, which in turns forces a refresh of the hw pointer and shows the buffer is empty. More specifically this patch makes a lot of sense when PulseAudio relies on timer-based scheduling to access audio devices such as HDAudio or Intel SST. Disabling interrupts removes two unwanted wake-ups due to period elapsed events in low-power playback modes. It also simplifies PulseAudio voice modules used for speech calls. To quote Lennart "This patch looks very interesting and desirable. This is something have long been waiting for." Support for this in hardware drivers is optional. Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@intel.com> Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core')
-rw-r--r--sound/core/pcm_lib.c6
-rw-r--r--sound/core/pcm_native.c3
2 files changed, 9 insertions, 0 deletions
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index b75db8e9cc0..bc57501c584 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -373,6 +373,11 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
(unsigned long)new_hw_ptr,
(unsigned long)runtime->hw_ptr_base);
}
+
+ /* without period interrupts, there are no regular pointer updates */
+ if (runtime->no_period_wakeup)
+ goto no_delta_check;
+
/* something must be really wrong */
if (delta >= runtime->buffer_size + runtime->period_size) {
hw_ptr_error(substream,
@@ -442,6 +447,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
(long)old_hw_ptr);
}
+ no_delta_check:
if (runtime->status->hw_ptr == new_hw_ptr)
return 0;
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 8bc7cb3db33..f91a439f675 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -423,6 +423,9 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
runtime->info = params->info;
runtime->rate_num = params->rate_num;
runtime->rate_den = params->rate_den;
+ runtime->no_period_wakeup =
+ (params->info & SNDRV_PCM_INFO_NO_PERIOD_WAKEUP) &&
+ (params->flags & SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP);
bits = snd_pcm_format_physical_width(runtime->format);
runtime->sample_bits = bits;