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

[Jayesh Choudhary <j-choudhary@ti.com>]

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


-jayesh

>> +		dpi0_out: endpoint {
>> +			remote-endpoint = <&dp0_in>;


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