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

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Message-ID: <f2f13082-20d6-4f22-8dfb-f11b01cd6706@oss.qualcomm.com>
Date: Wed, 13 Aug 2025 14:07:14 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Sarthak Garg <quic_sartgarg@...cinc.com>,
        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 1:56 PM, Krzysztof Kozlowski wrote:
> On 13/08/2025 13:21, Konrad Dybcio wrote:
>> 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
> 
> 
> You should double check. SM8450 (not v1!) needed it, so either it was
> copied to SM8550 (v2!) by mistake or was also needed.

I believe that the speed capabilities are indeed restricted on 8550-final
and that's why this patchset exists in the first place

Konrad