From: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com
Add new hw_params flag to explicitly tell driver that rewinds will never be used. This can be used by low-level driver to optimize DMA operations and reduce power consumption. Use this flag only when data written in ring buffer will never be invalidated, e.g. any update of appl_ptr is final.
Note that the update of appl_ptr include both a read/write data operation as well as snd_pcm_forward() whose behavior is not modified.
Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Signed-off-by: Ramesh Babu ramesh.babu@intel.com Signed-off-by: Subhransu S. Prusty subhransu.s.prusty@intel.com ---
v2 -> v3 return error for rewind operation if no_rewinds set.
include/sound/pcm.h | 1 + include/uapi/sound/asound.h | 1 + sound/core/pcm_native.c | 8 ++++++++ 3 files changed, 10 insertions(+)
diff --git a/include/sound/pcm.h b/include/sound/pcm.h index 79fedf517070..c1e2b87cd409 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -368,6 +368,7 @@ struct snd_pcm_runtime { unsigned int rate_num; unsigned int rate_den; unsigned int no_period_wakeup: 1; + unsigned int no_rewinds:1;
/* -- SW params -- */ int tstamp_mode; /* mmap timestamp is updated */ diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h index fd41697cb4d3..c697ff90450d 100644 --- a/include/uapi/sound/asound.h +++ b/include/uapi/sound/asound.h @@ -365,6 +365,7 @@ struct snd_pcm_info { #define SNDRV_PCM_HW_PARAMS_NORESAMPLE (1<<0) /* avoid rate resampling */ #define SNDRV_PCM_HW_PARAMS_EXPORT_BUFFER (1<<1) /* export buffer */ #define SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP (1<<2) /* disable period wakeups */ +#define SNDRV_PCM_HW_PARAMS_NO_REWINDS (1<<3) /* disable rewinds */
struct snd_interval { unsigned int min, max; diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index bf5d0f2acfb9..6769f4751fa0 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -554,6 +554,8 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream, runtime->no_period_wakeup = (params->info & SNDRV_PCM_INFO_NO_PERIOD_WAKEUP) && (params->flags & SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP); + runtime->no_rewinds = + (params->flags & SNDRV_PCM_HW_PARAMS_NO_REWINDS) ? 1 : 0;
bits = snd_pcm_format_physical_width(runtime->format); runtime->sample_bits = bits; @@ -2521,6 +2523,9 @@ static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst if (frames == 0) return 0;
+ if (runtime->no_rewinds) + return -ENODEV; + snd_pcm_stream_lock_irq(substream); ret = do_pcm_hwsync(substream); if (!ret) @@ -2539,6 +2544,9 @@ static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr if (frames == 0) return 0;
+ if (runtime->no_rewinds) + return -ENODEV; + snd_pcm_stream_lock_irq(substream); ret = do_pcm_hwsync(substream); if (!ret)