linux-kernel - Re: [PATCH RFC v2 1/4] dt-bindings: mmc: sdhci-of-dwcmhsc: Add T-Head TH1520 support

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Message-ID: <ZN1NBE2+HHfatQ/T@x1>
Date:   Wed, 16 Aug 2023 15:26:12 -0700
From:   Drew Fustini <dfustini@...libre.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Jisheng Zhang <jszhang@...nel.org>, Guo Ren <guoren@...nel.org>,
        Fu Wei <wefu@...hat.com>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Conor Dooley <conor@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
        Robert Nelson <robertcnelson@...gleboard.org>,
        Jason Kridner <jkridner@...gleboard.org>
Subject: Re: [PATCH RFC v2 1/4] dt-bindings: mmc: sdhci-of-dwcmhsc: Add
 T-Head TH1520 support

On Mon, Aug 07, 2023 at 08:29:21AM +0200, Krzysztof Kozlowski wrote:
> On 05/08/2023 05:14, Drew Fustini wrote:
> > Add compatible value for the T-Head TH1520 dwcmshc controller and
> > thead,io-fixed-1v8 and thead,pull-up properties.
> > 
> > Signed-off-by: Drew Fustini <dfustini@...libre.com>
> > ---
> >  Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml b/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml
> > index a43eb837f8da..57602c345cab 100644
> > --- a/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml
> > +++ b/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml
> > @@ -19,6 +19,7 @@ properties:
> >        - rockchip,rk3568-dwcmshc
> >        - rockchip,rk3588-dwcmshc
> >        - snps,dwcmshc-sdhci
> > +      - thead,th1520-dwcmshc
> >  
> >    reg:
> >      maxItems: 1
> > @@ -60,6 +61,14 @@ properties:
> >      description: Specify the number of delay for tx sampling.
> >      $ref: /schemas/types.yaml#/definitions/uint8
> >  
> > +  thead,io-fixed-1v8:
> > +    description: SoC PHY pad is fixed 1.8V
> > +    type: boolean
> 
> Isn't this duplicating existing properties for MMC modes with 1.8 V?

Thank you for reviewing. Yes, now that you mention it, I do see those
properties now in mmc-controller.yaml. It seems like the existing
mmc-ddr-1_8v property would be appropriate.

> 
> > +
> > +  thead,pull-up:
> > +    description: True if pull-up, false if pull-down
> 
> This explains me nothing. No clue what you are pulling and why do you
> need it. Pin pulls should be done via pin controller, not MMC.

Good point that my description is not helpful. The pull-up property
determines whether certain phy registers are written to. I need to try
to can get documentation on the phy so that I can better understand the
details of the pull-up configuration in the phy registers.

> 
> Anyway you should have here allOf:if:then (move the allOf: from top to
> behind "required:") which will disallow these properties for other variants.

I noticed that nvidia,tegra20-sdhci.yaml has several lines related to
pull-up/down configuration:

218   - if:
219       properties:
220         compatible:
221           contains:
222             const: nvidia,tegra210-sdhci
223     then:
224       properties:
225         pinctrl-names:
226           oneOf:
227             - items:
228                 - const: sdmmc-3v3
229                   description: pad configuration for 3.3 V
230                 - const: sdmmc-1v8
231                   description: pad configuration for 1.8 V
232                 - const: sdmmc-3v3-drv
233                   description: pull-up/down configuration for 3.3 V
234                 - const: sdmmc-1v8-drv
235                   description: pull-up/down configuration for 1.8 V
236             - items:
237                 - const: sdmmc-3v3-drv
238                   description: pull-up/down configuration for 3.3 V
239                 - const: sdmmc-1v8-drv
240                   description: pull-up/down configuration for 1.8 V
241             - items:
242                 - const: sdmmc-1v8-drv
243                   description: pull-up/down configuration for 1.8 V

Do you think creating something like that would be a good approach?

Thank you,
Drew