Re: [PATCH v9 4/5] arm64: dts: ti: k3-j784s4-evm: Enable DisplayPort-0

[Andrew Davis <afd@ti.com>]

On 8/7/23 7:56 AM, Aradhya Bhatia wrote:
> Hi Jayesh,
> 
> On 07-Aug-23 17:54, Jayesh Choudhary wrote:
>> Hello Aradhya,
>>
>> Thank you for the review.
>>
>> On 05/08/23 00:52, Aradhya Bhatia wrote:
>>> Hi Jayesh,
>>>
>>>
>>> On 03-Aug-23 13:34, Jayesh Choudhary wrote:
>>>> From: Rahul T R <r-ravikumar@ti.com>
>>>>
>>>> Enable display for J784S4 EVM.
>>>>
>>>> Add assigned clocks for DSS, DT node for DisplayPort PHY and pinmux for
>>>> DP HPD. Add the clock frequency for serdes_refclk.
>>>>
>>>> Add the endpoint nodes to describe connection from:
>>>> DSS => MHDP => DisplayPort connector.
>>>>
>>>> Also add the GPIO expander-4 node and pinmux for main_i2c4 which is
>>>> required for controlling DP power. Set status for all required nodes
>>>> for DP-0 as "okay".
>>>>
>>>> Signed-off-by: Rahul T R <r-ravikumar@ti.com>
>>>> [j-choudhary@ti.com: move all the changes together to enable DP-0 in
>>>> EVM]
>>>> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
>>>> ---
>>>>    arch/arm64/boot/dts/ti/k3-j784s4-evm.dts | 119 +++++++++++++++++++++++
>>>>    1 file changed, 119 insertions(+)
>>
>> [...]
>>
>>>> +        reg = <0>;
>>>> +        cdns,num-lanes = <4>;
>>>> +        #phy-cells = <0>;
>>>> +        cdns,phy-type = <PHY_TYPE_DP>;
>>>> +        resets = <&serdes_wiz4 1>, <&serdes_wiz4 2>,
>>>> +             <&serdes_wiz4 3>, <&serdes_wiz4 4>;
>>>> +    };
>>>> +};
>>>> +
>>>> +&mhdp {
>>>> +    status = "okay";
>>>> +    pinctrl-names = "default";
>>>> +    pinctrl-0 = <&dp0_pins_default>;
>>>> +    phys = <&serdes4_dp_link>;
>>>> +    phy-names = "dpphy";
>>>> +};
>>>> +
>>>> +&dss_ports {
>>>> +    port {
>>>
>>> Port index has not been added here. Since this port outputs to MHDP
>>> bridge, this should be "port@0", and a "reg = <0>;" property should be
>>> added below (along with the address and size cells properties).
>>>
>>> I suppose this works functionally in this case, because the port gets
>>> defaulted to "0" by the driver. But in future, when we add support for
>>> other dss output(s) on j784s4-evm, the driver will need indices to
>>> distinguish among them.
>>>
>>
>> Okay. It makes sense.
>> Just one thing here. Adding reg here would require it to have #address-
>> cells and #size-cell but since we have only single child port that too
>> at reg=<0>, it would throw dtbs_check warning:
>>
>> arch/arm64/boot/dts/ti/k3-j784s4-main.dtsi:1828.20-1831.5: Warning
>> (graph_child_address): /bus@100000/dss@4a00000/ports: graph node has
>> single child node 'port@0', #address-cells/#size-cells are not necessary
>>    also defined at arch/arm64/boot/dts/ti/k3-j784s4-evm.dts:911.12-919.3
>>
> 
> Okay! Was not aware about this. I still think "port@0" should be
> specified instead of just "port" and the warning should be ignored, if
> possible.
> 

Do not ignore new DT check warnings, if you go with "port@0" (which you
need to do as the "ti,j721e-dss" binding requires it) you must also add
the #address-cells/#size-cells.

Andrew

> If there were only a "port@1" child node, this warning would not have
> come up, and I believe "port@0" should be treated just the same.
> 
> Moreover, while we can add these properties at a later stage as an
> incremental patch, adding the size and address cells in the dtsi would
> affect other platform dts files as well, that use this SoC.
> 
> For e.g., the patch 5/5 of this series, on AM69-SK will still require
> the size and address cells for its ports. The clean up then will be that
> much more, when adding those incremental patches.
> 
> Anyway, I will let Nishanth and Vignesh take the final call on this.
> 
> Regards
> Aradhya
> 
>>
>>>> +        dpi0_out: endpoint {
>>>> +            remote-endpoint = <&dp0_in>;
>>
>>
>> [...]
>