Messages in this thread | | | Date | Mon, 7 Aug 2023 13:54:42 -0500 | Subject | Re: [PATCH v9 4/5] arm64: dts: ti: k3-j784s4-evm: Enable DisplayPort-0 | From | Andrew Davis <> |
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On 8/7/23 1:29 PM, Aradhya Bhatia wrote: > > > On 07-Aug-23 21:19, Andrew Davis wrote: >> 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. >> > > The warning that Jayesh mentioned above comes when "port@0" is > mentioned, *along-with* the #address-cells/#size-cells properties. > Essentially, it wants us to not use "port@0" when only single port is > being added whose reg values is 0. > > This warning does not come when only a single port other than 0, > "port@1" for e.g., is being used. That's the warning, that should get > ignored, if possible. >
Ah, I see now.
Almost seems like a bug in dtc checks, but checking the code it looks deliberate, although I cannot see why..
Rob,
Could you provide some guidance on why graph nodes are handled this way? Seems this is valid:
ports { #address-cells = <1>; #size-cells = <0>;
port@1 { reg = <1>; }; }
but this is not:
ports { #address-cells = <1>; #size-cells = <0>;
port@0 { reg = <0>; }; };
I'm guessing we allow port 0 to not be numbered if it is the only one for legacy convenience, but *forcing* it to not be numbered when it would otherwise be more consistent seems overly strict.
Andrew
> However, just mentioning "port@0", without the #address-cells/ > #size-cells, would be plain wrong. > > Regards > Aradhya > >> >>> 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>; >>>> >>>> >>>> [...] >>> >
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