Re: [linux-sunxi] [PATCH 05/16] ASoc: sun4i-i2s: Add 20 and 24 bit support

Samuel Holland
2020-07-10T05:46:30Z

On 7/4/20 6:38 AM, Clément Péron wrote:
> From: Marcus Cooper <codekipper@gmail.com>
>
> Extend the functionality of the driver to include support of 20 and
> 24 bits per sample.
>
> Signed-off-by: Marcus Cooper <codekipper@gmail.com>
> Signed-off-by: Clément Péron <peron.clem@gmail.com>
> ---
> sound/soc/sunxi/sun4i-i2s.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
> index f78167e152ce..bc7f9343bc7a 100644
> --- a/sound/soc/sunxi/sun4i-i2s.c
> +++ b/sound/soc/sunxi/sun4i-i2s.c
> @@ -577,6 +577,9 @@ static int sun4i_i2s_hw_params(struct snd_pcm_substream *substream,
> case 16:
> width = DMA_SLAVE_BUSWIDTH_2_BYTES;
> break;
> + case 32:
> + width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + break;

This breaks the sun4i variants, because sun4i_i2s_get_wss returns 4 for a 32 bit
width, but it needs to return 3.

As a side note, I wonder why we use the physical width (the spacing between
samples in RAM) to drive the slot width. S24_LE takes up 4 bytes per sample in
RAM, which we need for DMA. But I don't see why we would want to transmit the
padding over the wire. I would expect it to be transmitted the same as S24_3LE
(which has no padding). It did not matter before, because the only supported
format had no padding.

Regards,
Samuel

> default:
> dev_err(dai->dev, "Unsupported physical sample width: %d\n",
> params_physical_width(params));
> @@ -1063,6 +1066,10 @@ static int sun4i_i2s_dai_probe(struct snd_soc_dai *dai)
> return 0;
> }
>
> +#define SUN4I_FORMATS (SNDRV_PCM_FMTBIT_S16_LE | \
> + SNDRV_PCM_FMTBIT_S20_LE | \
> + SNDRV_PCM_FMTBIT_S24_LE)
> +
> static struct snd_soc_dai_driver sun4i_i2s_dai = {
> .probe = sun4i_i2s_dai_probe,
> .capture = {
> @@ -1070,14 +1077,14 @@ static struct snd_soc_dai_driver sun4i_i2s_dai = {
> .channels_min = 1,
> .channels_max = 8,
> .rates = SNDRV_PCM_RATE_8000_192000,
> - .formats = SNDRV_PCM_FMTBIT_S16_LE,
> + .formats = SUN4I_FORMATS,
> },
> .playback = {
> .stream_name = "Playback",
> .channels_min = 1,
> .channels_max = 8,
> .rates = SNDRV_PCM_RATE_8000_192000,
> - .formats = SNDRV_PCM_FMTBIT_S16_LE,
> + .formats = SUN4I_FORMATS,
> },
> .ops = &sun4i_i2s_dai_ops,
> .symmetric_rates = 1,