linux-kernel - Re: [PATCH V3 4/4] arm64: dts: qcom: sm8550: Remove SDR104/SDR50 broken capabilities

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Message-ID: <4038339c-a352-4007-85f5-44601a3578c2@kernel.org>
Date: Wed, 18 Jun 2025 11:08:10 +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 V3 4/4] arm64: dts: qcom: sm8550: Remove SDR104/SDR50
 broken capabilities

On 18/06/2025 10:44, Sarthak Garg wrote:
> 
> 
> On 6/18/2025 1:11 PM, Krzysztof Kozlowski wrote:
>> On 18/06/2025 09:28, Sarthak Garg wrote:
>>> Kernel now handles all level shifter limitations related to SD card
>>> modes.
>>> As a result, the broken hardware capabilities for SDR104 and SDR50 modes
>>> can be removed from the device tree.
>>> Additionally, due to level shifter constraints, set the maximum
>>> frequency for High Speed (HS) mode to 37.5 MHz using the
>>> max-sd-hs-frequency property for sm8550.
>>>
>>> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>
>>> ---
>>>   arch/arm64/boot/dts/qcom/sm8550.dtsi | 4 +---
>>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/sm8550.dtsi b/arch/arm64/boot/dts/qcom/sm8550.dtsi
>>> index 82cabf777cd2..2c770c979d39 100644
>>> --- a/arch/arm64/boot/dts/qcom/sm8550.dtsi
>>> +++ b/arch/arm64/boot/dts/qcom/sm8550.dtsi
>>> @@ -3180,6 +3180,7 @@ sdhc_2: mmc@...4000 {
>>>   			iommus = <&apps_smmu 0x540 0>;
>>>   			qcom,dll-config = <0x0007642c>;
>>>   			qcom,ddr-config = <0x80040868>;
>>> +			max-sd-hs-frequency = <37500000>;
>> So my previous comments stay... This is SoC thus deducible from compatible.
>>
>> Best regards,
>> Krzysztof
> 
> " I agree that a DT property for the mmc controller would make sense.
> 
> Although, this seems limited to SD UHS-I speed modes, so perhaps
> "max-sd-uhs-frequency" would be a better name for it?
> 
> Kind regards
> Uffe "
> 
> https://patchwork.kernel.org/project/linux-mmc/cover/20250523105745.6210-1-quic_sartgarg@quicinc.com/
> 
> This was the comment given on V2 to introduce a generic dt
> property.


I know, it does not matter. If this is here, it is a 100% proof this is
SoC specific, thus you have compatible for that.

Best regards,
Krzysztof