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

Jernej Škrabec
2020-09-02T18:07:40Z

Hi Samuel!

Dne petek, 10. julij 2020 ob 07:44:51 CEST je Samuel Holland napisal(a):
> 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.

I'm not sure what has WSS with physical width and DMA?

>
> 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.

Allwinner DMA engines support only 1, 2, 4 and sometimes 8 bytes for bus
width, so if sample is 24 bits in size, we have no other way but to transmit
padding too.

Best regards,
Jernej

>
> 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,