Re: [PATCH v2 2/2] dt-bindings: drm/bridge: Document Cadence DSI bridge bindings

[Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

On Tue, 13 Jun 2017 11:02:47 +0200
Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:

> Hi,
> 
> Just spotted this thread.
> 
> On 06.06.2017 14:58, Tomi Valkeinen wrote:
> > On 06/06/17 15:48, Boris Brezillon wrote:
> >  
> >> Okay. Thanks for the clarification. Can you confirm that this version
> >> is correct?
> >>
> >>  	dsi@xxx {
> >>  		#address-cells = <1>;
> >>  		#size-cells = <0>;
> >>  
> >>  		ports {
> >>  			#address-cells = <1>;
> >>  			#size-cells = <0>;
> >> 			dpi_in: port@0 {
> >>  				reg = <0>;
> >>  				#address-cells = <1>;
> >>  				#size-cells = <0>;
> >>  
> >>  				endpoint@0 {
> >>  					remote-endpoint = <&dpi_out>;
> >>  				};
> >>  			};
> >>  
> >>  			dsi_out: port@1 {
> >>  				reg = <1>;
> >> 				#address-cells = <1>;
> >>  				#size-cells = <0>;
> >>  
> >>  				dsi_out_vc0: endpoint@0 {
> >> 					reg = <0>;
> >>  					remote-endpoint = <&dsi_panel0_in>;
> >> 				};
> >>
> >>  				dsi_out_vc1: endpoint@1 {
> >> 					reg = <1>;
> >>  					remote-endpoint = <&dsi_panel1_in>;
> >>  				};
> >>  			};
> >>  		};
> >>  
> >>  		panel@0 {
> >>  			compatible = "...";
> >>  			reg = <0>;
> >>  			#address-cells = <1>;
> >>  			#size-cells = <0>;
> >>  
> >>  			port@0 {
> >>  				#address-cells = <1>;
> >>  		                #size-cells = <0>;
> >>  				reg = <0>;
> >>  
> >>  				dsi_panel0_in: endpoint@0 {
> >> 					reg = <0>;
> >>  					remote-endpoint = <&dsi_out_vc0>;
> >>  				};
> >>  			};
> >>  		};
> >>  
> >>  		panel@1 {
> >>  			compatible = "...";
> >>  			reg = <1>;
> >>  			#address-cells = <1>;
> >>  			#size-cells = <0>;
> >>  
> >>  			port@0 {
> >>  				#address-cells = <1>;
> >>  		                #size-cells = <0>;
> >>  				reg = <0>;
> >>  
> >>  				dsi_panel1_in: endpoint@0 {
> >> 					reg = <0>;
> >>  					remote-endpoint = <&dsi_out_vc1>;
> >>  				};
> >>  			};
> >>  		};
> >>  	};
> >>  
> > Looks correct to me. I think it can be a bit shorter though:
> >
> > - You don't need #address-cells and #size-cells for all. I think those
> > are inherited from the parent.
> > - If there's just one port and one endpoint, you can leave the 'reg'
> > out, as it's considered to be 0 by default.
> >
> > So for the panel, you can have just:
> >
> > port {
> > 	dsi_panel1_in: endpoint {
> > 		remote-endpoint = <&dsi_out_vc1>;
> > 	};
> > };  
> 
> In case DSI bus is used to both control and sending video signal you can
> skip video links from dsi-host to dsi-child, so nodes can look like:
> 
> 
>  	dsi@xxx {
>  		#address-cells = <1>;
>  		#size-cells = <0>;
>  
>  		ports {
>  			#address-cells = <1>;
>  			#size-cells = <0>;
> 			dpi_in: port@0 {
>  				reg = <0>;
>  				#address-cells = <1>;
>  				#size-cells = <0>;
>  
>  				endpoint@0 {
>  					remote-endpoint = <&dpi_out>;
>  				};
>  			};
>  
>  		};
>  
>  		panel@0 {
>  			compatible = "...";
>  			reg = <0>;
>  		};
>  
>  		panel@1 {
>  			compatible = "...";
>  			reg = <1>;
>  		};
>  	};
> 

Does that mean I should make port1 (AKA DSI ouput port) optional?
IMHO, it's clearer when these links are explicitly described in the DT,
but maybe there are good reasons to keep it implicit for the "control
through DSI" case.

Tomi, Archit, any opinion on this?

Regards,

Boris
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