80 lines
3.0 KiB
Diff
80 lines
3.0 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
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Date: Tue, 17 May 2016 14:00:15 +0530
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Subject: [PATCH] ALSA: core: let low-level driver or userspace disable rewinds
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Add new hw_params flag to explicitly tell driver that rewinds will never
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be used. This can be used by low-level driver to optimize DMA operations
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and reduce power consumption. Use this flag only when data written in
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ring buffer will never be invalidated, e.g. any update of appl_ptr is
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final.
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Note that the update of appl_ptr include both a read/write data
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operation as well as snd_pcm_forward() whose behavior is not modified.
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Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
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Signed-off-by: Ramesh Babu <ramesh.babu@intel.com>
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Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
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---
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include/sound/pcm.h | 1 +
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include/uapi/sound/asound.h | 1 +
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sound/core/pcm_native.c | 6 ++++++
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3 files changed, 8 insertions(+)
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diff --git a/include/sound/pcm.h b/include/sound/pcm.h
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index d6bd3caf6878..2eef65a9404e 100644
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--- a/include/sound/pcm.h
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+++ b/include/sound/pcm.h
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@@ -379,6 +379,7 @@ struct snd_pcm_runtime {
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unsigned int rate_num;
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unsigned int rate_den;
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unsigned int no_period_wakeup: 1;
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+ unsigned int no_rewinds:1;
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/* -- SW params -- */
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int tstamp_mode; /* mmap timestamp is updated */
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diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
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index ed0a120d4f08..ff57e4c89de4 100644
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--- a/include/uapi/sound/asound.h
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+++ b/include/uapi/sound/asound.h
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@@ -377,6 +377,7 @@ typedef int snd_pcm_hw_param_t;
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#define SNDRV_PCM_HW_PARAMS_NORESAMPLE (1<<0) /* avoid rate resampling */
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#define SNDRV_PCM_HW_PARAMS_EXPORT_BUFFER (1<<1) /* export buffer */
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#define SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP (1<<2) /* disable period wakeups */
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+#define SNDRV_PCM_HW_PARAMS_NO_REWINDS (1<<3) /* disable rewinds */
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struct snd_interval {
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unsigned int min, max;
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diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
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index db62dbe7eaa8..56ab147c8429 100644
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--- a/sound/core/pcm_native.c
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+++ b/sound/core/pcm_native.c
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@@ -727,6 +727,8 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
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runtime->no_period_wakeup =
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(params->info & SNDRV_PCM_INFO_NO_PERIOD_WAKEUP) &&
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(params->flags & SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP);
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+ runtime->no_rewinds =
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+ (params->flags & SNDRV_PCM_HW_PARAMS_NO_REWINDS) ? 1 : 0;
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bits = snd_pcm_format_physical_width(runtime->format);
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runtime->sample_bits = bits;
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@@ -2673,11 +2675,15 @@ static snd_pcm_sframes_t rewind_appl_ptr(struct snd_pcm_substream *substream,
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static snd_pcm_sframes_t snd_pcm_rewind(struct snd_pcm_substream *substream,
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snd_pcm_uframes_t frames)
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{
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+ struct snd_pcm_runtime *runtime = substream->runtime;
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snd_pcm_sframes_t ret;
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if (frames == 0)
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return 0;
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+ if (runtime->no_rewinds)
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+ return 0;
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+
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snd_pcm_stream_lock_irq(substream);
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ret = do_pcm_hwsync(substream);
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if (!ret)
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--
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https://clearlinux.org
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