linux-kernel - Re: [PATCH v6 2/5] arm64: dts: qcom: Add sdhc dll-presets

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Message-ID: <b98eb114-6967-4ac4-8b4d-936966a58171@quicinc.com>
Date: Tue, 16 Dec 2025 18:11:32 +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>, <quic_pragalla@...cinc.com>,
        <quic_sayalil@...cinc.com>, <quic_nitirawa@...cinc.com>,
        <quic_bhaskarv@...cinc.com>, <kernel@....qualcomm.com>
Subject: Re: [PATCH v6 2/5] arm64: dts: qcom: Add sdhc dll-presets

On 12/15/2025 5:37 PM, Krzysztof Kozlowski wrote:
> On 15/12/2025 13:05, Krzysztof Kozlowski wrote:
>> On 15/12/2025 13:00, Ram Prakash Gupta wrote:
>>> Add sdhc dll-presets for qdu1000 target.
>>>
>>> Signed-off-by: Ram Prakash Gupta <quic_rampraka@...cinc.com>
>>> ---
>>>  arch/arm64/boot/dts/qcom/qdu1000.dtsi | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> Please use subject prefixes matching the subsystem. You can get them for
>> example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
>> your patch is touching. For bindings, the preferred subjects are
>> explained here:
>> https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters

sure I missed to add qdu1000:, will add in subject.

>>> diff --git a/arch/arm64/boot/dts/qcom/qdu1000.dtsi b/arch/arm64/boot/dts/qcom/qdu1000.dtsi
>>> index 846e5e5899aa..bc31504d5c8c 100644
>>> --- a/arch/arm64/boot/dts/qcom/qdu1000.dtsi
>>> +++ b/arch/arm64/boot/dts/qcom/qdu1000.dtsi
>>> @@ -912,8 +912,8 @@ sdhc: mmc@...4000 {
>>>  
>>>  			bus-width = <8>;
>>>  
>>> -			qcom,dll-config = <0x0007642c>;
>>> -			qcom,ddr-config = <0x80040868>;
>>> +			qcom,dll-presets = <0x000F64EC 0x0 0x01	0x2C010800 0x80040868>,
>>> +					   <0x0007642C 0x0 0x10 0x2C010800 0x80040868>;
>>
>> That's non-bisectable. You just broke the users of this DTS. Also, case
>> change is not explained and your binding said nothing about deprecating
>> other properties.

right I will update the sequence of dt as last change in the series.

I couldn't get "case change is not explained" but I guess ask is for
explanation why is this change needed. As the soc is using artanis
dll, it needs to have 3 more register values as presets. So in total
2 arrays, for HS400 and HS200, are passed each having 5 elements,
DLL_CONFIG, DLL_CONFIG_2, DLL_CONFIG_3, DLL_USER_CTRL & DDR_CONFIG.
Without these sampling of data would not be optimal and might lead
to CRC errors.

The existing qcom,dll-config or qcom-ddr-config are not deprecated,
as upcoming soc could still be non-artanis and only dll-config and
ddr-config might be needed. But since it was added earlier in qdu1000,
removing it now as the code change is pushed into driver to support
dll-presets.

with QDU1000 there were instance of CRC errors and to fix dll-presets
is used instead of qcom,dll-config & qcom,ddr-config.

I will update the binding as well with more details.

>
> Also, your binding said 10 items, not two.
>
>
> Best regards,
> Krzysztof

Sorry I mistook the elements of array with Items. Will update in binding
to 2 items.