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authorJaroslav Kysela <perex@perex.cz>2010-08-18 14:16:54 +0200
committerJaroslav Kysela <perex@perex.cz>2010-08-19 09:15:24 +0200
commitd7d28bc29f4ea7c2d23ed002a9973c64a92bcdb8 (patch)
tree74bd0f5fc69f1b2b937921d01dcc5e3b52b77efc
parent597603d615d2b19a9e451d8cfac24372856a522d (diff)
ALSA: pcm midlevel code - add time check for double interrupt acknowledge
The current code in pcm_lib.c do all checks using only the position in the ring buffer. Unfortunately, where the interrupts gets delayed or merged into one, we need another timing source to check when the buffer size boundary overlaps to avoid the wrong updating of the ring buffer pointers. This code uses jiffies to check the right time window without any performance impact. Signed-off-by: Jaroslav Kysela <perex@perex.cz>
-rw-r--r--include/sound/pcm.h1
-rw-r--r--sound/core/pcm_lib.c14
-rw-r--r--sound/core/pcm_native.c2
3 files changed, 12 insertions, 5 deletions
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index dd76cdede64d..54c4ccf6fec2 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -274,6 +274,7 @@ struct snd_pcm_runtime {
snd_pcm_uframes_t hw_ptr_base; /* Position at buffer restart */
snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time */
unsigned long hw_ptr_jiffies; /* Time when hw_ptr is updated */
+ unsigned long hw_ptr_buffer_jiffies; /* buffer time in jiffies */
snd_pcm_sframes_t delay; /* extra delay; typically FIFO size */
/* -- HW params -- */
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index e9d98be190c5..d6ecca27bb68 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -329,11 +329,15 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
/* delta = "expected next hw_ptr" for in_interrupt != 0 */
delta = runtime->hw_ptr_interrupt + runtime->period_size;
if (delta > new_hw_ptr) {
- hw_base += runtime->buffer_size;
- if (hw_base >= runtime->boundary)
- hw_base = 0;
- new_hw_ptr = hw_base + pos;
- goto __delta;
+ /* check for double acknowledged interrupts */
+ hdelta = jiffies - runtime->hw_ptr_jiffies;
+ if (hdelta > runtime->hw_ptr_buffer_jiffies/2) {
+ hw_base += runtime->buffer_size;
+ if (hw_base >= runtime->boundary)
+ hw_base = 0;
+ new_hw_ptr = hw_base + pos;
+ goto __delta;
+ }
}
}
/* new_hw_ptr might be lower than old_hw_ptr in case when */
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 303ac04ff6e4..2d2e1b65ee9a 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -867,6 +867,8 @@ static void snd_pcm_post_start(struct snd_pcm_substream *substream, int state)
struct snd_pcm_runtime *runtime = substream->runtime;
snd_pcm_trigger_tstamp(substream);
runtime->hw_ptr_jiffies = jiffies;
+ runtime->hw_ptr_buffer_jiffies = (runtime->buffer_size * HZ) /
+ runtime->rate;
runtime->status->state = state;
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
runtime->silence_size > 0)