linux-kernel - Re: [PATCH v2 1/6] dt-bindings: spi: sun6i: add DT bindings for Allwinner R329 SPI

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Message-ID: <20230506225811.4e928e46@slackpad.lan>
Date:   Sat, 6 May 2023 22:58:11 +0100
From:   Andre Przywara <andre.przywara@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Maksim Kiselev <bigunclemax@...il.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Cristian Ciocaltea <cristian.ciocaltea@...labora.com>,
        Heiko Stuebner <heiko.stuebner@...ll.eu>,
        Maxime Ripard <mripard@...nel.org>, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 1/6] dt-bindings: spi: sun6i: add DT bindings for
 Allwinner R329 SPI

On Sat, 6 May 2023 12:53:07 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

Hi Maksim,

> On 06/05/2023 09:30, Maksim Kiselev wrote:
> > From: Icenowy Zheng <icenowy@...c.io>
> > 
> > Allwinner R329 SPI has two controllers, and the second one has helper
> > functions for MIPI-DBI Type C.  
> 
> I wonder what is the difference of DBI compatible. You refer to "helper
> functions", which sounds like driver... do you mean some parts of SPI
> controller?

So I checked the manuals, all of the D1, T113-s and R329 are the same
in this respect:
- There are two SPI controllers, the "first" one is what this series
  fully supports.
- The second SPI controller has some additional registers and two
  extra bits in the control register to drive the DBI extension, but is
  otherwise compatible to the first one:

So I'd suggest to introduce the following compatible string
combinations to the binding *now*. We don't support the DBI bits (yet),
but this would be the correct hardware description:

For the R329:
spi0: spi@...5000 {
	compatible = "allwinner,sun50i-r329-spi";
	....
spi1: spi@...6000 {
	compatible = "allwinner,sun50i-r329-spi-dbi",
		     "allwinner,sun50i-r329-spi";
For the D1/T113s:
spi0: spi@...5000 {
	compatible = "allwinner,sun20i-d1-spi",
		     "allwinner,sun50i-r329-spi";
	....
spi1: spi@...6000 {
	compatible = "allwinner,sun20i-d1-spi-dbi",
		     "allwinner,sun50i-r329-spi-dbi",
		     "allwinner,sun50i-r329-spi";

I leave that as an exercise to the reader to convert that into the
minimal set of DT schema lines ;-)
I would suggest to add both the D1/T113s and the R329 bindings in this
one patch, to reduce the churn. I guess if you do this, you could even
drop Icenowy's authorship on this patch, since it has not much to do
with the original version anymore.

Cheers,
Andre


> > Add compatible strings for these controllers
> > 
> > Signed-off-by: Icenowy Zheng <icenowy@...c.io>
>
> > ---
> >  .../devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml        | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml b/Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml
> > index de36c6a34a0f..2c1b8da35339 100644
> > --- a/Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml
> > +++ b/Documentation/devicetree/bindings/spi/allwinner,sun6i-a31-spi.yaml
> > @@ -21,6 +21,8 @@ properties:
> >      oneOf:
> >        - const: allwinner,sun6i-a31-spi
> >        - const: allwinner,sun8i-h3-spi
> > +      - const: 
> > +      - const: allwinner,sun50i-r329-spi-dbi  
> 
> As Conor pointed out, nothing improved here.
> 
> Best regards,
> Krzysztof
>