Device-Tree bindings for LVDS Display Bridge (ldb)

LVDS Display Bridge
===================

The LVDS Display Bridge device tree node contains up to two lvds-channel
nodes describing each of the two LVDS encoder channels of the bridge.

Required properties:
 - #address-cells : should be <1>
 - #size-cells : should be <0>
 - compatible : should be "fsl,imx53-ldb" or "fsl,imx6q-ldb".
                Both LDB versions are similar, but i.MX6 has an additional
                multiplexer in the front to select any of the four IPU display
                interfaces as input for each LVDS channel.
 - gpr : should be <&gpr> on i.MX53 and i.MX6q.
         The phandle points to the iomuxc-gpr region containing the LVDS
         control register.
- clocks, clock-names : phandles to the LDB divider and selector clocks and to
                        the display interface selector clocks, as described in
                        Documentation/devicetree/bindings/clock/clock-bindings.txt
        The following clocks are expected on i.MX53:
                "di0_pll" - LDB LVDS channel 0 mux
                "di1_pll" - LDB LVDS channel 1 mux
                "di0" - LDB LVDS channel 0 gate
                "di1" - LDB LVDS channel 1 gate
                "di0_sel" - IPU1 DI0 mux
                "di1_sel" - IPU1 DI1 mux
        On i.MX6q the following additional clocks are needed:
                "di2_sel" - IPU2 DI0 mux
                "di3_sel" - IPU2 DI1 mux
        The needed clock numbers for each are documented in
        Documentation/devicetree/bindings/clock/imx5-clock.yaml, and in
        Documentation/devicetree/bindings/clock/imx6q-clock.yaml.

Optional properties:
 - pinctrl-names : should be "default" on i.MX53, not used on i.MX6q
 - pinctrl-0 : a phandle pointing to LVDS pin settings on i.MX53,
               not used on i.MX6q
 - fsl,dual-channel : boolean. if it exists, only LVDS channel 0 should
   be configured - one input will be distributed on both outputs in dual
   channel mode

LVDS Channel
============

Each LVDS Channel has to contain either an of graph link to a panel device node
or a display-timings node that describes the video timings for the connected
LVDS display as well as the fsl,data-mapping and fsl,data-width properties.

Required properties:
 - reg : should be <0> or <1>
 - port: Input and output port nodes with endpoint definitions as defined in
   Documentation/devicetree/bindings/graph.txt.
   On i.MX5, the internal two-input-multiplexer is used. Due to hardware
   limitations, only one input port (port@[0,1]) can be used for each channel
   (lvds-channel@[0,1], respectively).
   On i.MX6, there should be four input ports (port@[0-3]) that correspond
   to the four LVDS multiplexer inputs.
   A single output port (port@2 on i.MX5, port@4 on i.MX6) must be connected
   to a panel input port. Optionally, the output port can be left out if
   display-timings are used instead.

Optional properties (required if display-timings are used):
 - display-timings : A node that describes the display timings as defined in
   Documentation/devicetree/bindings/display/panel/display-timing.txt.
 - fsl,data-mapping : should be "spwg" or "jeida"
                      This describes how the color bits are laid out in the
                      serialized LVDS signal.
 - fsl,data-width : should be <18> or <24>

example:

gpr: iomuxc-gpr@53fa8000 {
	/* ... */
};

ldb: ldb@53fa8008 {
	#address-cells = <1>;
	#size-cells = <0>;
	compatible = "fsl,imx53-ldb";
	gpr = <&gpr>;
	clocks = <&clks IMX5_CLK_LDB_DI0_SEL>,
		 <&clks IMX5_CLK_LDB_DI1_SEL>,
		 <&clks IMX5_CLK_IPU_DI0_SEL>,
		 <&clks IMX5_CLK_IPU_DI1_SEL>,
		 <&clks IMX5_CLK_LDB_DI0_GATE>,
		 <&clks IMX5_CLK_LDB_DI1_GATE>;
	clock-names = "di0_pll", "di1_pll",
		      "di0_sel", "di1_sel",
		      "di0", "di1";

	/* Using an of-graph endpoint link to connect the panel */
	lvds-channel@0 {
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <0>;

		port@0 {
			reg = <0>;

			lvds0_in: endpoint {
				remote-endpoint = <&ipu_di0_lvds0>;
			};
		};

		port@2 {
			reg = <2>;

			lvds0_out: endpoint {
				remote-endpoint = <&panel_in>;
			};
		};
	};

	/* Using display-timings and fsl,data-mapping/width instead */
	lvds-channel@1 {
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <1>;
		fsl,data-mapping = "spwg";
		fsl,data-width = <24>;

		display-timings {
			/* ... */
		};

		port@1 {
			reg = <1>;

			lvds1_in: endpoint {
				remote-endpoint = <&ipu_di1_lvds1>;
			};
		};
	};
};

panel: lvds-panel {
	/* ... */

	port {
		panel_in: endpoint {
			remote-endpoint = <&lvds0_out>;
		};
	};
};