linux-kernel - Re: [alsa-devel] [PATCH v2 1/7] ASoC: fsl_sai: Add registers definition for multiple datalines

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Date:   Mon, 29 Jul 2019 22:57:43 +0300
From:   Daniel Baluta <daniel.baluta@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     Daniel Baluta <daniel.baluta@....com>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Timur Tabi <timur@...nel.org>, Rob Herring <robh@...nel.org>,
        "S.j. Wang" <shengjiu.wang@....com>,
        "Angus Ainslie (Purism)" <angus@...ea.ca>,
        Takashi Iwai <tiwai@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        Viorel Suman <viorel.suman@....com>,
        Fabio Estevam <festevam@...il.com>,
        Mihai Serban <mihai.serban@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [alsa-devel] [PATCH v2 1/7] ASoC: fsl_sai: Add registers
 definition for multiple datalines

On Mon, Jul 29, 2019 at 10:42 PM Nicolin Chen <nicoleotsuka@...il.com> wrote:
>
> On Sun, Jul 28, 2019 at 10:24:23PM +0300, Daniel Baluta wrote:
> > SAI IP supports up to 8 data lines. The configuration of
> > supported number of data lines is decided at SoC integration
> > time.
> >
> > This patch adds definitions for all related data TX/RX registers:
> >       * TDR0..7, Transmit data register
> >       * TFR0..7, Transmit FIFO register
> >       * RDR0..7, Receive data register
> >       * RFR0..7, Receive FIFO register
> >
> > Signed-off-by: Daniel Baluta <daniel.baluta@....com>
> > ---
> >  sound/soc/fsl/fsl_sai.c | 76 +++++++++++++++++++++++++++++++++++------
> >  sound/soc/fsl/fsl_sai.h | 36 ++++++++++++++++---
> >  2 files changed, 98 insertions(+), 14 deletions(-)
> >
> > diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> > index 6d3c6c8d50ce..17b0aff4ee8b 100644
> > --- a/sound/soc/fsl/fsl_sai.c
> > +++ b/sound/soc/fsl/fsl_sai.c
>
> > @@ -704,7 +711,14 @@ static bool fsl_sai_readable_reg(struct device *dev, unsigned int reg)
> >       case FSL_SAI_TCR3:
> >       case FSL_SAI_TCR4:
> >       case FSL_SAI_TCR5:
> > -     case FSL_SAI_TFR:
> > +     case FSL_SAI_TFR0:
> > +     case FSL_SAI_TFR1:
> > +     case FSL_SAI_TFR2:
> > +     case FSL_SAI_TFR3:
> > +     case FSL_SAI_TFR4:
> > +     case FSL_SAI_TFR5:
> > +     case FSL_SAI_TFR6:
> > +     case FSL_SAI_TFR7:
> >       case FSL_SAI_TMR:
> >       case FSL_SAI_RCSR:
> >       case FSL_SAI_RCR1:
>
> A tricky thing here is that those SAI instances on older SoC don't
> support multi data lines physically, while seemly having registers
> pre-defined. So your change doesn't sound doing anything wrong to
> them at all, I am still wondering if it is necessary to apply them
> to newer compatible only though, as for older compatibles of SAI,
> these registers would be useless and confusing if being exposed.
>
> What do you think?

Yes, I thought about this too. But, I tried to keep the code as short
as possible and technically it is not wrong. When 1 data line is supported
for example application will only care about TDR0, TFR0, etc.