From: Laxmi Devi Laxmi.Devi@in.bosch.com
These changes are required due to the kernel commit 07b7acb51d283d8469696c906b91f1882696a4d4 ("ASoC: rsnd: update pointer more accurate")
Issue is that snd_pcm_wait() goes back to waiting because the hw_ptr is not period aligned. Therefore snd_pcm_wait() will block for a longer time as required.
With these rcar driver changes the exact position of the dma is returned. During snd_pcm_start they read hw_ptr as reference, and this hw_ptr is now not period aligned, and is a little ahead over the period while it is read. Therefore when the avail is calculated during snd_pcm_wait(), it is missing the avail_min by a few frames. Consider the below example:
Considering the application is trying to write 0x120 frames and the period_size = 0x60, avail_min = 0x120 and buffersize = 0x360 :
rsnd_pointer=0x12c -> dma pointer at the end of second write during snd_pcm_dmix_start(). Since another 0x120 buffer is available, application writes 0x120 and goes to snd_pcm_wait(). It is woken up after 3 snd_pcm_period_elapsed() to see rsnd_pointer=0x248. So hw_ptr = new_slave_hw_ptr - reference_slave_hw_ptr = 0x248 - 0x12c = 0x11c. It needs 4 more frames to be able to write. And so it goes back to waiting.
But since 3 snd_pcm_period_elapsed(), 3 periods should be available and it should have been able to write. If rsnd_pointer during the start was 0x120 which is 3 periods then 0x248 - 0x120 = 128 it could go on with write.
Signed-off-by: Laxmi Devi Laxmi.Devi@in.bosch.com Signed-off-by: Timo Wischer twischer@de.adit-jv.com ---
With this patch the slave_hw_ptr will always contain a period align value.
src/pcm/pcm_dmix.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c index 881154e..6c9e052 100644 --- a/src/pcm/pcm_dmix.c +++ b/src/pcm/pcm_dmix.c @@ -398,6 +398,8 @@ static int snd_pcm_dmix_sync_ptr0(snd_pcm_t *pcm, snd_pcm_uframes_t slave_hw_ptr snd_pcm_sframes_t diff; old_slave_hw_ptr = dmix->slave_hw_ptr; + slave_hw_ptr = ((slave_hw_ptr / dmix->slave_period_size) + * dmix->slave_period_size); dmix->slave_hw_ptr = slave_hw_ptr; diff = slave_hw_ptr - old_slave_hw_ptr; if (diff == 0) /* fast path */ @@ -560,6 +562,8 @@ static int snd_pcm_dmix_hwsync(snd_pcm_t *pcm) static void reset_slave_ptr(snd_pcm_t *pcm, snd_pcm_direct_t *dmix) { dmix->slave_appl_ptr = dmix->slave_hw_ptr = *dmix->spcm->hw.ptr; + dmix->slave_hw_ptr = ((dmix->slave_hw_ptr / dmix->slave_period_size) + * dmix->slave_period_size); if (pcm->buffer_size > pcm->period_size * 2) return; /* If we have too litte periods, better to align the start position