QTI Snapdragon Display Engine (SDE) shared display

Snapdragon Display Engine shared display provids the capability to virtualize
one physical connector to multiple virtual connectors sit at different blend
stages. Each virtual connector can be attached to different CRTCs and commit
independently.

This device must be added to the connectors list of qcom,sde-kms device.

Required properties:
- compatible:		"qcom,shared-display"
- qcom,shared-display-base: node handle of qcom,shared-display-base, see below.
- qcom,blend-stage-range: A pair of u32 property <start size> defines the blend
			stage start and size for the shared display. For example
			<4 5> indicates this shared display's blending stage starts
			from 4 and there are 5 stages in total. Different shared
			display located on the same base display should not overlap
			with their blend stages. The maximum stages should be within
			the range of layer mixer hardware capability.

Optional properties:
- qcom,shared-display-src-mode: source resolution of the shared display, which is also
			the framebuffer size. It contains two properties:
			qcom,mode-h-active: A u32 property defines horizontal resolution.
			qcom,mode-v-active: A u32 property defines vertical resolution.
			If qcom,shared-display-src-mode is not defined, horizontal and
			vertical resolution will be the same as base display, and
			qcom,shared-display-dst-mode will be ignored.
- qcom,shared-display-dst-mode: destination rectangle in the shared display, which also
			includes the padding lines if line padding feature is enabled.
			It contains 4 properties:
			qcom,mode-x-offset: A u32 property of x offset.
			qcom,mode-y-offset: A u32 property of y offset.
			qcom,mode-width: A u32 property of width.
			qcom,mode-height: A u32 property of height, including line padding.
- qcom,shared-display-name:  A string used as a descriptive name of the shared display.
			If qcom,shared-display-name is not defined, a system auto-generated
			name will be used like DSI-X or DP-X.

qcom,shared-display-base properties:

Required properties:
- qcom,shared-display-base-intf: A u32 property defines intf index of the base display.
			If qcom,shared-display-base-intf is defined,
			qcom,shared-display-base-connector will be ignored.
- qcom,shared-display-base-connector: A string property defines connector name of the base
			display. It is another way to identify the base connector when
			qcom,shared-display-base-intf is not defined.

Optional properties:
- qcom,shared-display-base-mst: A u32 property defines the DP MST branch port, needed if
			the base display sits on DP MST display. Only used when
			qcom,shared-display-base-intf is defined.
- qcom,shared-display-base-mode: timing of the physical base display, contains the
			following properties:
			qcom,mode-h-active: A u32 property defines the horizontal active size.
			qcom,mode-h-front-porch: A u32 property defines the horizontal front porch.
			qcom,mode-h-pulse-width: A u32 property defines the horizontal pulse.
			qcom,mode-h-back-porch: A u32 property defines the horizontal back porch.
			qcom,mode-h-active-high: A boolean property defines if horizontal polarity
						is high.
			qcom,mode-v-active: A u32 property defines the vertical active size.
			qcom,mode-v-front-porch: A u32 property defines the vertical front portch.
			qcom,mode-v-pulse-width: A u32 property defines the vertical pulse width.
			qcom,mode-v-back-porch: A u32 property defines the vertical back porch.
			qcom,mode-v-active-high: A boolean property defines if vertical polarity
						is high.
			qcom,mode-refresh-rate: A u32 property defines vertial refresh rate.
			qcom,mode-clock-in-khz: A u32 property defines clock in kHz.
			If qcom,shared-display-base-mode is not defined, auto-detected mode
			from panel will be used as base mode.

Example of static mode using intf to select base connector:

/ {
	...

	sde_sh_base0: qcom,shared-display-base@0 {
		qcom,shared-display-base-intf = <0>;
		qcom,shared-display-base-mode {
			qcom,mode-h-active = <3840>;
			qcom,mode-h-front-porch = <176>;
			qcom,mode-h-pulse-width = <88>;
			qcom,mode-h-back-porch = <296>;
			qcom,mode-h-active-high;
			qcom,mode-v-active = <2160>;
			qcom,mode-v-front-porch = <8>;
			qcom,mode-v-pulse-width = <10>;
			qcom,mode-v-back-porch = <72>;
			qcom,mode-v-active-high;
			qcom,mode-refresh-rate = <30>;
			qcom,mode-clock-in-khz = <297000>;
		};
	};

	sde_sh0: qcom,shared-display@0 {
		compatible = "qcom,shared-display";
		qcom,shared-display-base = <&sde_sh_base0>;
		qcom,blend-stage-range = <0 5>;
		qcom,shared-display-name = "shared-disp-0";
		qcom,shared-display-src-mode {
			qcom,mode-h-active = <1920>;
			qcom,mode-v-active = <2160>;
		};
		qcom,shared-display-dst-mode {
			qcom,mode-x-offset = <0>;
			qcom,mode-y-offset = <0>;
			qcom,mode-width = <1920>;
			qcom,mode-height = <2160>;
		};
	};

	sde_sh1: qcom,shared-display@1 {
		compatible = "qcom,shared-display";
		qcom,shared-display-base = <&sde_sh_base0>;
		qcom,blend-stage-range = <5 5>;
		qcom,shared-display-name = "shared-disp-1";
		qcom,shared-display-src-mode {
			qcom,mode-h-active = <1920>;
			qcom,mode-v-active = <2160>;
		};
		qcom,shared-display-dst-mode {
			qcom,mode-x-offset = <1920>;
			qcom,mode-y-offset = <0>;
			qcom,mode-width = <1920>;
			qcom,mode-height = <2160>;
		};
	};
};

Example of dynamic mode using name to select base connector:

/ {
	...

	sde_sh_base0: qcom,shared-display-base@0 {
		qcom,shared-display-base-connector = "DSI-1";
	};

	sde_sh0: qcom,shared-display@0 {
		compatible = "qcom,shared-display";
		qcom,shared-display-base = <&sde_sh_base0>;
		qcom,blend-stage-range = <0 5>;
		qcom,shared-display-name = "shared-disp-0";
	};

	sde_sh1: qcom,shared-display@1 {
		compatible = "qcom,shared-display";
		qcom,shared-display-base = <&sde_sh_base0>;
		qcom,blend-stage-range = <5 5>;
		qcom,shared-display-name = "shared-disp-1";
	};
};