linux-kernel - Re: [PATCH v3 1/4] ASoC: fsl_asrc: Change asrc_width to asrc

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Date:   Thu, 27 Feb 2020 22:40:09 -0800
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Shengjiu Wang <shengjiu.wang@...il.com>
Cc:     Shengjiu Wang <shengjiu.wang@....com>,
        Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        Timur Tabi <timur@...nel.org>, Xiubo Li <Xiubo.Lee@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/4] ASoC: fsl_asrc: Change asrc_width to asrc_format

On Fri, Feb 28, 2020 at 10:54:02AM +0800, Shengjiu Wang wrote:
> Hi
> 
> On Fri, Feb 28, 2020 at 1:45 AM Nicolin Chen <nicoleotsuka@...il.com> wrote:
> >
> > On Thu, Feb 27, 2020 at 01:10:19PM +0800, Shengjiu Wang wrote:
> > > On Thu, Feb 27, 2020 at 11:43 AM Nicolin Chen <nicoleotsuka@...il.com> wrote:
> > > >
> > > > On Thu, Feb 27, 2020 at 10:41:55AM +0800, Shengjiu Wang wrote:
> > > > > asrc_format is more inteligent variable, which is align
> > > > > with the alsa definition snd_pcm_format_t.
> > > > >
> > > > > Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> > > > > ---
> > > > >  sound/soc/fsl/fsl_asrc.c     | 23 +++++++++++------------
> > > > >  sound/soc/fsl/fsl_asrc.h     |  4 ++--
> > > > >  sound/soc/fsl/fsl_asrc_dma.c |  2 +-
> > > > >  3 files changed, 14 insertions(+), 15 deletions(-)
> > > > >
> > > > > diff --git a/sound/soc/fsl/fsl_asrc.c b/sound/soc/fsl/fsl_asrc.c
> > > > > index 0dcebc24c312..2b6a1643573c 100644
> > > > > --- a/sound/soc/fsl/fsl_asrc.c
> > > > > +++ b/sound/soc/fsl/fsl_asrc.c
> > > >
> > > > > @@ -600,11 +599,6 @@ static int fsl_asrc_dai_hw_params(struct snd_pcm_substream *substream,
> > > > >
> > > > >       pair->config = &config;
> > > > >
> > > > > -     if (asrc_priv->asrc_width == 16)
> > > > > -             format = SNDRV_PCM_FORMAT_S16_LE;
> > > > > -     else
> > > > > -             format = SNDRV_PCM_FORMAT_S24_LE;
> > > >
> > > > It feels better to me that we have format settings in hw_params().
> > > >
> > > > Why not let fsl_easrc align with this? Any reason that I'm missing?
> > >
> > > because the asrc_width is not formal,  in the future we can direct
> >
> > Hmm..that's our DT binding. And I don't feel it is a problem
> > to be ASoC irrelative.
> >
> > > input the format from the dts. format involve the info about width.
> >
> > Is there such any formal ASoC binding? I don't see those PCM
> > formats under include/dt-bindings/ folder. How are we going
> > to involve those formats in DT?
> 
> There is no formal binding of this case.
> 
> I think it is not good to convert width to format, because, for example

The thing is that fsl_easrc does the conversion too... It just
does in the probe instead of hw_params(), and then copies them
in the hw_params(). So I don't see obvious benefit by doing so.

> width = 24,  there is two option, we can select format S24_LE,  or
> format S24_3LE,  width is ambiguous for selecting.
> 
> In EASRC, it support other two 24bit format U24_LE, U24_3LE .

I understood the reason here, but am not seeing the necessity,
at this point.

> if we use the format in DT, then it is clear for usage in driver.

I think this is the thing that we should address first. If we
have such a binding being added with the new fsl_easrc driver,
I'd love to see the old driver aligning with the new one.

Otherwise, we can keep the old way, and change it when the new
binding is ready.