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

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Message-ID: <dda9a2ef-5b86-4883-8347-b5ccf25e8d5d@quicinc.com>
Date: Thu, 14 Aug 2025 12:45:18 +0530
From: Sarthak Garg <quic_sartgarg@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.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 8/13/2025 5:37 PM, Konrad Dybcio wrote:
> 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

Hi Krzysztof, Konrad,

Konrad is right — this patch series addresses limitations seen on
SM8550-final silicon.

SDR50 mode: The tuning support introduced in this series helps ensure
reliable operation.
SDR104 mode: limitations are resolved in SM8550 v2.

But still to avoid regressions, *I’ll like to retain sdhci-caps-mask in
sm8550.dtsi for now and revisit its removal for future targets after
thorough validation and testing from the beginning.*

Konrad suggested placing max-sd-hs-frequency in the SoC dtsi.
Krzysztof, could you please share your thoughts on this approach?

Best regards,
Sarthak Garg