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

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Message-ID: <8b023e56-435b-43df-8b15-c562a494e06f@kernel.org>
Date: Tue, 5 Aug 2025 11:25:40 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 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 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