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Fri, 22 Sep 2023 08:18:13 -0700 (PDT) Received: from x1 ([2601:1c2:1800:f680:c44:77f:ca7d:adec]) by smtp.gmail.com with ESMTPSA id 6-20020a170902e9c600b001c1f4edfb87sm3614450plk.92.2023.09.22.08.18.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Sep 2023 08:18:13 -0700 (PDT) Date: Fri, 22 Sep 2023 08:18:11 -0700 From: Drew Fustini To: Conor Dooley Cc: Ulf Hansson , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Jisheng Zhang , Adrian Hunter , Guo Ren , Fu Wei , Paul Walmsley , Palmer Dabbelt , Albert Ou , Robert Nelson , Jason Kridner , Xi Ruoyao , Han Gao , Icenowy Zheng , linux-mmc@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH 1/6] dt-bindings: mmc: sdhci-of-dwcmhsc: Add T-Head TH1520 support Message-ID: References: <20230921-th1520-mmc-v1-0-49f76c274fb3@baylibre.com> <20230921-th1520-mmc-v1-1-49f76c274fb3@baylibre.com> <20230922-parish-ice-a22e93dc3027@spud> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230922-parish-ice-a22e93dc3027@spud> Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org On Fri, Sep 22, 2023 at 10:57:36AM +0100, Conor Dooley wrote: > Hey Drew, > > On Thu, Sep 21, 2023 at 06:49:48PM -0700, Drew Fustini wrote: > > Add compatible value for the T-Head TH1520 dwcmshc controller and add > > thead,phy-pull-up property. > > > > Signed-off-by: Drew Fustini > > --- > > Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml b/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml > > index a43eb837f8da..46b768d46712 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 +61,9 @@ properties: > > description: Specify the number of delay for tx sampling. > > $ref: /schemas/types.yaml#/definitions/uint8 > > > > + thead,phy-pull-up: > > + description: Enable weak pull-up on PHY pads > > + type: boolean > > Why is the weak pull-up required? How would the dts author know if they > need to use this property? This is a good question, and I don't have a good reason beyond it is what the vendor SDK was doing. There are only two boards right now using the TH1520 that I know of. Both the LPi4a [1] and the Ahead [2] have the pull-up property set on all the mmc controller nodes their downstream device trees. Rob suggested on #devicetree that it would be simpler to just enable it in the driver and disable support when needed. I like this idea as it will simplify this binding patch and the code in the driver patch. Thanks, Drew [1] https://git.beagleboard.org/beaglev-ahead/BeagleBoard-DeviceTrees/-/blob/v5.10.x-ti-unified/src/riscv/light-beagle-ref.dts [2] https://github.com/revyos/thead-kernel/blob/lpi4a/arch/riscv/boot/dts/thead/light-lpi4a-ref.dts