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

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Message-ID: <4091c488-996c-4318-82ad-c054a9ef5a22@oss.qualcomm.com>
Date: Wed, 13 Aug 2025 13:21:20 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Sarthak Garg <quic_sartgarg@...cinc.com>,
        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>
Cc: 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 8/13/25 1:08 PM, Sarthak Garg wrote:
> 
> 
> On 8/5/2025 2:55 PM, Krzysztof Kozlowski wrote:
>> On 05/08/2025 11:19, 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 ---
>>>>>    4 files changed, 3 insertions(+), 3 deletions(-)
>>>>>
>>>>
>>>> This will break MMC for all of the users and nothing in commit msg or
>>>> cover letter explains that or mentions merging strategy.
>>>>
>>>> Exactly this case is covered by your internal guideline, no? Please read it.
>>>>
>>>> Best regards,
>>>> Krzysztof
>>>
>>> Just to make sure I’m addressing the right concern — are you primarily
>>> worried about the introduction of the max-sd-hs-frequency property in
>>> the board DTS files, or about the removal of the sdhci-caps-mask
>>> from the common sm8550.dtsi?
>>
>>
>> Apply this patch and test MMC. Does it work? No. Was it working? Yes.
>>
>>
>> Best regards,
>> Krzysztof
> 
> 
> You're absolutely right to raise the concern about potential breakage.
> After conducting additional testing across multiple boards, I’ve confirmed that the removal of SDR104/SDR50 broken capabilities does indeed affect V1 SM8550 devices.

v1 is a prototype revision, please forget it exists, we most definitely
do not support it upstream

Konrad


> However, on V2 devices, all modes—including SDR104, SDR50, and HS—are fully functional and have been verified to work reliably.
> 
> Based on your feedback, I will revise the patch to retain the broken SDR104/SDR50 capabilities in the common sm8550.dtsi, ensuring no impact on current sm8550 devices already in use.
> 
> We will revisit the removal of broken capabilities dt property for upcoming targets after thorough validation and testing to ensure no regressions from the beginning.
> 
> Please let me know if this approach aligns with your expectations. I’ll prepare and send out a revised patch accordingly.
> 
> Best regards,
> Sarthak