linux-kernel - Re: [PATCH v6 1/5] dt-bindings: mmc: Add dll-presets values for HS400 and HS200 modes

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Message-ID: <00485066-d537-4f8f-a579-efa33e69a56f@quicinc.com>
Date: Tue, 16 Dec 2025 18:21:05 +0530
From: Ram Prakash Gupta <quic_rampraka@...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>,
        <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH v6 1/5] dt-bindings: mmc: Add dll-presets values for HS400
 and HS200 modes


On 12/15/2025 5:41 PM, Krzysztof Kozlowski wrote:
> On 15/12/2025 13:06, Krzysztof Kozlowski wrote:
>> On 15/12/2025 13:00, Ram Prakash Gupta wrote:
>>> From: Sachin Gupta <quic_sachgupt@...cinc.com>
>>>
>>> Document the 'dll-presets' property for MMC device tree bindings.
>>> The 'dll-presets' property defines the DLL configurations for HS400
>>> and HS200 modes.
>>>
>>> QC SoCs can have 0 to 4 SDHCI instances, and each one may need
>>> different tuning.
>>>
>>> Signed-off-by: Sachin Gupta <quic_sachgupt@...cinc.com>
>>> Signed-off-by: Ram Prakash Gupta <quic_rampraka@...cinc.com>
>>> ---
>>>  Documentation/devicetree/bindings/mmc/sdhci-msm.yaml | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.yaml b/Documentation/devicetree/bindings/mmc/sdhci-msm.yaml
>>> index 938be8228d66..a1a16e6e12ce 100644
>>> --- a/Documentation/devicetree/bindings/mmc/sdhci-msm.yaml
>>> +++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.yaml
>>> @@ -140,6 +140,11 @@ properties:
>>>      $ref: /schemas/types.yaml#/definitions/uint32
>>>      description: platform specific settings for DLL_CONFIG reg.
>>>  
>>> +  qcom,dll-presets:
>>> +    maxItems: 10
>>> +    $ref: /schemas/types.yaml#/definitions/uint32-array
>>> +    description: platform specific settings for DLL registers.
>>
>> So look at your DTS - this is clearly incomplete now. So obvious. I
>> don't understand why you were hiding the DTS change, you just make
>> review more difficult.
>>
>> Anyway, your DTS says you replace some other DLL properties and nothing
>> in the binding or commit msg explains that. Neither the reason nor the
>> impact.

Sorry dt change was not pushed earlier, will add dt change as well
going forward.

The existing qcom,dll-config or qcom-ddr-config are not deprecated,
but certainly I will add below in commit regarding the issue as well
which is observed without this change as below:

"Document the 'dll-presets' property for MMC device tree bindings.
The 'dll-presets' property defines the DLL configurations for HS400
and HS200 modes.

It have 2 arrays of 5 elements each for HS400 and HS200 mode.
The 5 elements are DLL_CONFIG, DLL_CONFIG_2,DLL_CONFIG_3, DLL_USER_CTRL
and DDR_CONFIG.

dll-presets fixes instances of CRC error observed with targets having
artanis dll.

QC SoCs can have 0 to 4 SDHCI instances, and each one may need
different tuning using dll-presets."

> Plus it looks like you are adding some meaning to the entries, judging
> by the DTS. DTS suggested something here is e.g. DLL_CONFIG, so that
> meaning - including different modes - needs description in the schema in
> items.
>
> Best regards,
> Krzysztof

I will update the schema description as well with the 2 modes and 5 elements
of it and will update the MaxItems to 2.

Thanks,
Ram