hints around rcar_lvds.c :)

[Tommaso Merciai <tomm.merciai@xxxxxxxxx>]

Hi Laurent, All,

Sorry for bothering.
Looking for some feedback :)

I have a similar rcar_lvds.c IP's to handle but in my case:
I have lvds0 and lvds1 that are sharing some common regs (lvds_cmn).

 ----------------------
|    -------------     |
|   |lvds_cmn_regs|    |
|    -------------     |
|                      |
|    -----------       |
|   | lvds0_regs |     |-----> ch0
|    ------------      |
|                      |
|    -----------       |
|   | lvds1_regs |     |-----> ch1
|    ------------      |
 ----------------------


So I'm checking 2 drm dts/driver architecture:

1st architecture:
 - Using a single lvds driver to handle both lvds0 and lvds1.

		 ----------------------
		|                      |
		|                      |
		|                      |
du_lvds0 ------>|                      |----> ch0_lvds
		|      lvds_bridge     |
		|                      |
		|                      |
du_lvds1 ------>|                      |----> ch1_lvds
		|                      |
		 ----------------------


Issue:

Problem here is the 1 single link 2ch mode.
lvds0 and lvds1 can drive 2 display with 2 differents fb (fb0 and fb1).

Having a single drm_bridge to drive both channel give me the following issue:

In single link 2ch mode when for the first time the du encoder drm_attach()
the lvds bridge to the encoder(du) all goes fine and fb0 is created correctly.

Then again the du encoder is trying again to drm_attach() the lvds bridge
but this return -EBUSY obviously because is already attached.

Then I think this is not the way to follow because I need 2 drm_bridges
from the same drm drive, and I think this is not correct.
----------

2nd architecture:
 - Follow rcar_lvds.c way using 2 nodes for lvds0 and lvds1:

		 ------------
du_lvds0 -----> |lvds0_bridge|----> ch0_lvds
		 ------------

		 ------------
du_lvds1 -----> |lvds1_bridge|----> ch1_lvds
		 ------------

Issue:
I thinks this is an optimal approach but in my case here
the problem is that lvds0 and lvds1 share a set of common registers
some common clocks and common reset:

My plan is to manipulate those common regs (lvds_cmn) using
compatible = "simple-mfd", "syscon"; as follow:

lvds_cmn: lvds-cmn {
	compatible = "simple-mfd", "syscon";
	reg = <common_regs>;

	lvds0: lvds0-encoder {

		ports {
			#address-cells = <1>;
			#size-cells = <0>;
			clocks = <&common_clk>, <&dotclok0>, <&phyclock0>;
			resets = <&common_rst>;

			port@0 {
				reg = <0>;
				lvds0_in: endpoint {
					remote-endpoint = <&du_out_lvds0>;
				};
			};

			port@1 {
				reg = <1>;
				lvds_ch0: endpoint {
				};
			};
		};
	};

	lvds1: lvds1-encoder {

		ports {
			#address-cells = <1>;
			#size-cells = <0>;
			clocks = <&common_clk>, <&dotclok1>, <&phyclock1>;
                        resets = <&common_rst>;

			port@0 {
				reg = <0>;
				lvds1_in: endpoint {
					remote-endpoint = <&du_out_lvds1>;
				};
			};

			port@1 {
				reg = <1>;
				lvds_ch1: endpoint {
				};
			};
		};
	};
};
----------

I'm asking to find the best way to represent those IP's.
What do you think?
Any hints/tips would be nice.
Thanks in advance.

Thanks & Regards,
Tommaso