linux-kernel - Re: [PATCH V4 2/4] dt-bindings: mmc: controller: Add max-sd-hs-frequency property

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Message-ID: <b43cb2fd-c583-4383-9b2a-c186ac1c4e09@quicinc.com>
Date: Fri, 1 Aug 2025 16:11:29 +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 V4 2/4] dt-bindings: mmc: controller: Add
 max-sd-hs-frequency property



On 8/1/2025 2:30 PM, Krzysztof Kozlowski wrote:
> On 01/08/2025 10:45, Sarthak Garg wrote:
>> Some platforms may require limiting the maximum frequency used in SD
>> High-Speed (HS) mode due to board-level hardware constraints. For
>> example, certain boards may include level shifters or other components
>> that cannot reliably operate at the default 50 MHz HS frequency.
>>
>> Introduce a new optional device tree property max-sd-hs-frequency to
>> limit the maximum frequency (in Hz) used for SD cards operating in
>> High-Speed (HS) mode.
>>
>> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>
>> ---
>>   .../devicetree/bindings/mmc/mmc-controller-common.yaml | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>> index 9a7235439759..6c2529b976d1 100644
>> --- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>> +++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>> @@ -93,6 +93,16 @@ properties:
>>       minimum: 400000
>>       maximum: 384000000
>>   
>> +  max-sd-hs-frequency:
> 
> Use standard unit suffixes. s/frequency/hz/
> 
> 
> 

Sure will update this name to max-sd-hs-hz in V5.

>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description: |
>> +      Maximum frequency (in Hz) to be used for SD cards operating in
>> +      High-Speed (HS) mode. This is useful for board-specific limitations,
>> +      such as level shifters or others where the card cannot reliably
>> +      operate at the default 50 MHz HS frequency.
> 
> Don't repeat constraints in free form text.
> 
> default:
> 
> 

Sure will remove min/max constraints and add default: 50000000 in V5.