linux-kernel - Re: [PATCH V3 2/7] dt-bindings: spi: Add compatible for MT7986 with single mode

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Message-ID: <7ae469a94ad51be85f0731c4c42088d65b241581.camel@mediatek.com>
Date:   Tue, 8 Mar 2022 09:51:36 +0800
From:   Leilk Liu <leilk.liu@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        "Mark Brown" <broonie@...nel.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-spi@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
        "Rob Herring" <robh@...nel.org>
Subject: Re: [PATCH V3 2/7] dt-bindings: spi: Add compatible for MT7986 with
 single mode

On Mon, 2022-03-07 at 11:32 +0100, AngeloGioacchino Del Regno wrote:
> Il 07/03/22 07:52, Leilk Liu ha scritto:
> > This patch adds dt-binding documentation for MT7986 with single
> > mode.
> > 
> > Signed-off-by: Leilk Liu <leilk.liu@...iatek.com>
> > Acked-by: Rob Herring <robh@...nel.org>
> > ---
> >   Documentation/devicetree/bindings/spi/mediatek,spi-mt65xx.yaml |
> > 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/spi/mediatek,spi-
> > mt65xx.yaml b/Documentation/devicetree/bindings/spi/mediatek,spi-
> > mt65xx.yaml
> > index bfa44acb1bdd..48024b98408a 100644
> > --- a/Documentation/devicetree/bindings/spi/mediatek,spi-
> > mt65xx.yaml
> > +++ b/Documentation/devicetree/bindings/spi/mediatek,spi-
> > mt65xx.yaml
> > @@ -41,6 +41,7 @@ properties:
> >                 - mediatek,mt8135-spi
> >                 - mediatek,mt8173-spi
> >                 - mediatek,mt8183-spi
> > +              - mediatek,mt7986-spi-single
> >   
> >     reg:
> >       maxItems: 1
> 
> I think that the best way to do this is to better organize the
> compatibles
> per-hardware, here... or the compatibles list will eventually grow
> out of
> control for little reason.
> 
> Since "IPM" is a new SPI controller IP, I would expect more and more
> MediaTek
> SoCs using it in the future, so here's my proposal:
Yes, we plan to use this IP with new ICs.

> 
> - Add a generic (const) compatible "mediatek,spi-ipm" to describe the
> hardware
> - Add an enumeration with "mediatek,mt7986-spi-ipm" as the only
> member, as to
>    prepare this binding for the future.
> - Single and quad mode can be expressed with generic SPI bindings!
> 
> Specifically, you can express that with "spi-rx-bus-width" for
> SPI_RX_{....}
> and "spi-tx-bus-width" for SPI_TX_{....}, so you don't need different
> compatibles
> for "mediatek,mt7986-spi-single" and "mediatek,mt7896-spi-quad".
> 
> Fast example:
> 
> spi@...45678 {
>      compatible = "mediatek,mt7986-spi-ipm", "mediatek,spi-ipm";
>      reg = <....>
>      /* Quad mode */
>      spi-rx-bus-width = <4>;
>      spi-tx-bus-width = <4>;
> 
>      .... etc ....
> }
> 
OK, thanks for your advice.

> Regards,
> Angelo
> 
>