At Thu, 17 Dec 2009 15:00:02 +0900,
jassisinghbrar@xxxxxxxxx wrote:
>
> From: Jassi Brar <jassi.brar@xxxxxxxxxxx>
>
> The check for at least 'avail_min' available data before calling wake_up
> doesn't always hold good as it does not guarantee callbacks at each periodic
> interrupt.
Well, avail_min can be greater than period_size. And, avail_min won't be
less than period size.
For example, when avail_min = 2.5 x period_size, the driver wakes up
in periods like 3, 2, 3, 2, ...
> An example of such situation is snd_pcm_lib_read1/write1 consuming some space
> of the period and going to sleep from wait_for_avail_min upon syncing with
> the DMA pointer. Clearly just the remainder of period size is needed, but
> wake_up is called only after _two_ periodic interrupts from that point.
In that case, the original behavior is correct.
thanks,
Takashi
>
> Signed-off-by: Jassi Brar <jassi.brar@xxxxxxxxxxx>
> ---
> sound/core/pcm_lib.c | 10 ++++++++--
> 1 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> index 30f4108..ee2d7b9 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -189,7 +189,7 @@ snd_pcm_update_hw_ptr_pos(struct snd_pcm_substream *substream,
> static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
> struct snd_pcm_runtime *runtime)
> {
> - snd_pcm_uframes_t avail;
> + snd_pcm_uframes_t avail, prd_short;
>
> if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> avail = snd_pcm_playback_avail(runtime);
> @@ -208,8 +208,14 @@ static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
> return -EPIPE;
> }
> }
> - if (avail >= runtime->control->avail_min)
> +
> + prd_short = runtime->period_size
> + - runtime->status->hw_ptr % runtime->period_size;
> +
> + if (avail >= runtime->control->avail_min
> + || avail >= prd_short)
> wake_up(&runtime->sleep);
> +
> return 0;
> }
>
> --
> 1.6.2.5
>
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