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SubjectRe: [PATCH 11/13] ARM: dts: stm32: fix LTDC port node on STM32 MCU ad MPU
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On 4/15/21 4:30 PM, Marek Vasut wrote:
> On 4/15/21 3:34 PM, Alexandre TORGUE wrote:
>> Hi Marek
>
> Hello Alexandre,
>
>>>> diff --git a/arch/arm/boot/dts/stm32mp157c-dk2.dts
>>>> b/arch/arm/boot/dts/stm32mp157c-dk2.dts
>>>> index 2bc92ef3aeb9..19ef475a48fc 100644
>>>> --- a/arch/arm/boot/dts/stm32mp157c-dk2.dts
>>>> +++ b/arch/arm/boot/dts/stm32mp157c-dk2.dts
>>>> @@ -82,9 +82,15 @@
>>>>   };
>>>>   &ltdc {
>>>> -    status = "okay";
>>>> -
>>>>       port {
>>>> +        #address-cells = <1>;
>>>> +        #size-cells = <0>;
>>>> +
>>>> +        ltdc_ep0_out: endpoint@0 {
>>>> +            reg = <0>;
>>>> +            remote-endpoint = <&sii9022_in>;
>>>> +        };
>>>> +
>>>>           ltdc_ep1_out: endpoint@1 {
>>>>               reg = <1>;
>>>>               remote-endpoint = <&dsi_in>;
>>>
>>> [...]
>>>
>>>> diff --git a/arch/arm/boot/dts/stm32mp15xx-dhcor-avenger96.dtsi
>>>> b/arch/arm/boot/dts/stm32mp15xx-dhcor-avenger96.dtsi
>>>> index 64dca5b7f748..e7f10975cacf 100644
>>>> --- a/arch/arm/boot/dts/stm32mp15xx-dhcor-avenger96.dtsi
>>>> +++ b/arch/arm/boot/dts/stm32mp15xx-dhcor-avenger96.dtsi
>>>> @@ -277,11 +277,7 @@
>>>>       status = "okay";
>>>>       port {
>>>> -        #address-cells = <1>;
>>>> -        #size-cells = <0>;
>>>> -
>>>> -        ltdc_ep0_out: endpoint@0 {
>>>> -            reg = <0>;
>>>> +        ltdc_ep0_out: endpoint {
>>>>               remote-endpoint = <&adv7513_in>;
>>>>           };
>>>>       };
>>>
>>> I think this is wrong, the AV96 can have two displays connected to
>>> two ports of the LTDC, just like DK2 for example.
>>
>> As for dk2 address/size cells are added only if there are 2 endpoints.
>> It is for this reason I moved endpoint0 definition from
>> stm32mp15xx-dkx to stm32mp151a-dk1.dts (dk1 has only one endpoint).
>>
>> Here it's the same, if you have second endpoint then adress/size will
>> have to be added.
>
> That's a bit problematic. Consider either the use case of DTO which adds
> the other display, or even a custom board DTS. Without your patch, this
> works:
>
> arch/arm/boot/dts/stm32mp15xx-dhcor-avenger96.dtsi
> &ltdc {
>   ...
>   ports {
>     ltdc_ep0_out: endpoint@0 {
>       remote-endpoint = <&adv7513_in>;
>     };
>   };
> };
>
> board-with-display.dts or board-overlay.dts
> &ltdc {
>   ports {
>     endpoint@1 { // just add another endpoint@1, no problem
>       remote-endpoint = <&display>;
>     };
>   };
> };
>
> With your patch, the DTS would have to modify the "endpoint" node to be
> "endpoint@0" probably with a whole lot of /detele-node/ etc. magic (DTO
> cannot do that, so that's a problem, and I do use DTOs on AV96
> extensively for the various expansion cards) and then add the
> endpoint@1. That becomes real complicated in custom board DT, and
> impossible with DTO.

Yes I agree that it'll be problematic. So maybe so solution would be to
not detect a warning for the initial case (only one endpoint with a reg)

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