linux-kernel - Re: [PATCH V4 4/4] arm64: dts: qcom: sm8550: Remove SDR104/SDR50 broken capabilities

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Message-ID: <5d5820c5-463a-4fa0-8ad9-21b75797aaf9@oss.qualcomm.com>
Date: Tue, 5 Aug 2025 15:08:06 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Sarthak Garg <quic_sartgarg@...cinc.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, quic_cang@...cinc.com,
        quic_nguyenb@...cinc.com, quic_rampraka@...cinc.com,
        quic_pragalla@...cinc.com, quic_sayalil@...cinc.com,
        quic_nitirawa@...cinc.com, quic_bhaskarv@...cinc.com,
        kernel@....qualcomm.com
Subject: Re: [PATCH V4 4/4] arm64: dts: qcom: sm8550: Remove SDR104/SDR50
 broken capabilities

On 8/5/25 11:59 AM, Dmitry Baryshkov wrote:
> On Tue, Aug 05, 2025 at 02:49:29PM +0530, Sarthak Garg wrote:
>>
>>
>> On 8/1/2025 2:32 PM, Krzysztof Kozlowski wrote:
>>> On 01/08/2025 10:45, Sarthak Garg wrote:
>>>> The kernel now handles level shifter limitations affecting SD card
>>>> modes, making it unnecessary to explicitly disable SDR104 and SDR50
>>>> capabilities in the device tree.
>>>>
>>>> However, due to board-specific hardware constraints particularly related
>>>> to level shifter in this case the maximum frequency for SD High-Speed
>>>> (HS) mode must be limited to 37.5 MHz to ensure reliable operation of SD
>>>> card in HS mode. This is achieved using the max-sd-hs-frequency property
>>>> in the board DTS.
>>>>
>>>> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>
>>>> ---
>>>>   arch/arm64/boot/dts/qcom/sm8550-hdk.dts                     | 1 +
>>>>   arch/arm64/boot/dts/qcom/sm8550-mtp.dts                     | 1 +
>>>>   arch/arm64/boot/dts/qcom/sm8550-sony-xperia-yodo-pdx234.dts | 1 +
>>>>   arch/arm64/boot/dts/qcom/sm8550.dtsi                        | 3 ---
> 
> You missed several devices which use SM8550. Please fix that.

I would be in favor of making this addition in the SoC dtsi and removing/
altering it on a case by case basis, since as I explained in the threads
of previous revisions, the fix for the limitation is additional on-board
hardware

Konrad