Any suggestion for this patch?
On Mon, 2015-09-14 at 14:51 +0800, Koro Chen wrote:
> In capture, there is chance that hw_ptr reported at IRQ is
> a little smaller than period_size due to internal AFE buffer.
> In the case of ping-pong buffer:
>
> |xxxxxxxxxxxxxxxxxxxxxxxxxxxx--|-----------------------------|
> hw_ptr < period_size
>
> This available buffer will not be read since its size is smaller than
> avail_min (which is period_size by default), and read thread continues
> to sleep. If the next hw_ptr is just a little larger than buffer_size,
> overrun occurs. One more period can hold the possible unread buffer.
>
> Signed-off-by: Koro Chen <koro.c...@mediatek.com>
> ---
> sound/soc/mediatek/mtk-afe-pcm.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/sound/soc/mediatek/mtk-afe-pcm.c
> b/sound/soc/mediatek/mtk-afe-pcm.c
> index d190fe0..f5baf3c 100644
> --- a/sound/soc/mediatek/mtk-afe-pcm.c
> +++ b/sound/soc/mediatek/mtk-afe-pcm.c
> @@ -549,6 +549,23 @@ static int mtk_afe_dais_startup(struct snd_pcm_substream
> *substream,
> memif->substream = substream;
>
> snd_soc_set_runtime_hwparams(substream, &mtk_afe_hardware);
> +
> + /*
> + * Capture cannot use ping-pong buffer since hw_ptr at IRQ may be
> + * smaller than period_size due to AFE's internal buffer.
> + * This easily leads to overrun when avail_min is period_size.
> + * One more period can hold the possible unread buffer.
> + */
> + if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
> + ret = snd_pcm_hw_constraint_minmax(runtime,
> + SNDRV_PCM_HW_PARAM_PERIODS,
> + 3,
> +
> mtk_afe_hardware.periods_max);
> + if (ret < 0) {
> + dev_err(afe->dev, "hw_constraint_minmax failed\n");
> + return ret;
> + }
> + }
> ret = snd_pcm_hw_constraint_integer(runtime,
> SNDRV_PCM_HW_PARAM_PERIODS);
> if (ret < 0)
--
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