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

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Message-ID: <a93fb5bf-1fd5-4e00-8338-b8608a9ba8fa@kernel.org>
Date: Wed, 13 Aug 2025 13:56:36 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 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 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.


Best regards,
Krzysztof