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

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Message-ID: <86ad5ddb-1a43-45c3-af35-9eb863c66f63@quicinc.com>
Date: Wed, 18 Jun 2025 14:14:58 +0530
From: Sarthak Garg <quic_sartgarg@...cinc.com>
To: 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 V3 4/4] arm64: dts: qcom: sm8550: Remove SDR104/SDR50
 broken capabilities



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.

Best regards,
Sarthak