linux-kernel - Re: [PATCH v3 1/1] arm64: dts: qcom: sm8550: remove address/size-cells from mdss

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Date: Wed, 20 Dec 2023 08:10:15 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: "Aiqun Yu (Maria)" <quic_aiquny@...cinc.com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Tengfei Fan <quic_tengfan@...cinc.com>, andersson@...nel.org,
 konrad.dybcio@...aro.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, kernel@...cinc.com
Subject: Re: [PATCH v3 1/1] arm64: dts: qcom: sm8550: remove
 address/size-cells from mdss_dsi1

On 20/12/2023 01:53, Aiqun Yu (Maria) wrote:
> 
> 
> On 12/19/2023 6:21 PM, Dmitry Baryshkov wrote:
>> On Tue, 19 Dec 2023 at 12:09, Aiqun Yu (Maria) <quic_aiquny@...cinc.com> wrote:
>>>
>>>
>>>
>>> On 12/19/2023 5:41 PM, Krzysztof Kozlowski wrote:
>>>> On 19/12/2023 10:36, Aiqun Yu (Maria) wrote:
>>>>>
>>>>>
>>>>> On 12/19/2023 3:17 PM, Krzysztof Kozlowski wrote:
>>>>>> On 19/12/2023 01:31, Tengfei Fan wrote:
>>>>>>> The address/size-cells in mdss_dsi1 node have not ranges and child also
>>>>>>> have not reg, then this leads to dtc W=1 warnings:
>>>>>>
>>>>> Comments can be more readable:
>>>>> "mdss_dsi1" node don't have "ranges" or child "reg" property, while it
>>>>> have address/size-cells properties. This caused
>>>>> "avoid_unnecessary_addr_size" warning from dtb check.
>>>>> Remove address/size-cells properties for "mdss_dsi1" node.
>>>>>
>>>>>> I cannot parse it. Address/size cells never have ranges or children.
>>>>>> They cannot have. These are uint32 properties.
>>>>> Pls help to comment on the revised commit message. Every time I write a
>>>>> commit message, also takes a while for me to double confirm whether
>>>>> others can understand me correctly as well. Feel free to let us know if
>>>>> it is not readable to you. It will help us as non-English native developers.
>>>>>>
>>>>>>>
>>>>>>>      sm8550.dtsi:2937.27-2992.6: Warning (avoid_unnecessary_addr_size): /soc@...isplay-subsystem@...0000/dsi@...6000:
>>>>>>>        unnecessary #address-cells/#size-cells without "ranges" or child "reg" property
>>>>>>>
>>>>>>>
>>>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>>>>>> Signed-off-by: Tengfei Fan <quic_tengfan@...cinc.com>
>>>>>>> ---
>>>>>>
>>>>>> I disagreed with the patch before. You resubmit it without really
>>>>>> addressing my concerns.
>>>>>>
>>>>>> I am not sure if this is correct fix and I want to fix all of such
>>>>>> errors (there are multiple of them) in the same way. Feel free to
>>>>>> propose common solution based on arguments.
>>>>> Per my understanding, "qcom,mdss-dsi-ctrl" driver node like "mdss_dsi1"
>>>>> don't need to have address/size-cells properties.
>>>>
>>>> Just because dtc says so? And what about bindings?
>>> I don't find any reason why "qcom,mdss-dsi-ctrl" driver node need to
>>> have address/size-cells properties. Document Bindings should also be fixed.
>>>>
>>>>> Feel free to let us know whether there is different idea of
>>>>> "address/size-cells" needed for the "qcom,mdss-dsi-ctrl" driver node.
>>>>
>>>> The bindings expressed that idea. If the binding is incorrect, fix the
>>>> binding and the DTS. If the binding is correct, provide rationale why it
>>>> somehow does not apply here etc.
>>> Our plan is to fix the bindings as well.
>>>
>>> In case you have missed the question, I just re-place it here:
>>> While there are about 22 different soc dtsi and it's document binding
>>> files needed to be fixed. Shall we fix it for all qcom related soc usage
>>> in one patch, or we'd better to split into different patches according
>>> to soc specifically?
>>
>> Don't touch the bindings unless you understand what you are doing.
>> Your patch will be NAKed. There can be a DSI panel attached to the DSI
>> host, which means there is a need for #address-cells / #size-cells.
>>
> Could you please help to elaborate more on details? Like what's the 
> right example here for the "qcom,mdss-dsi-ctrl" driver node needed to 
> have "#address-cells"/"#size-cells".

Isn't the binding describing such example?

> 
> Thx to chime in that we have put a good amount of time here.
>> Please stop wasting the time on dtc warning. The bindings (and the
>> file) are correct.
> I don't agree here.
> Either it is a wrong usage of "#address-cells"/"#size-cells", or dtc 
> warning should be fixed with this usage take into account.
> "dtb check" will be a good guideline for developers to follow, I don't 
> think it is wasting time here.

You don't agree but you don't know how this binding works?

Best regards,
Krzysztof