disp: msm: dp: add dp-mst sideband simulator

Add sideband simulator aux bridge to re-direct sideband message
from aux channel to internal emulation software stack. When this
bridge is connected to DP device, simulator will read ports configuration
from device tree and fake all sideband messages.

Change-Id: Ib8af2e0f4ba9b0d02413d40b796e5006b376ada8
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>
Signed-off-by: Karim Henain <khenain@codeaurora.org>
Signed-off-by: Sudarsan Ramesh <sudarame@codeaurora.org>

Documentation/devicetree/bindings/drm/msm/sde-dp-sim.txt

@@ -0,0 +1,58 @@
+QTI Snapdragon Display Engine (SDE) DP-MST sideband message emulation driver
+
+Required properties:
+- compatible:		"qcom,dp-mst-sim"
+
+Each child node represents a port at root branch, with 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 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 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.
+
+Example:
+
+/ {
+	...
+
+	sde_dp_mst_sim: qcom,dp-mst-sim {
+		compatible = "qcom,dp-mst-sim";
+
+		port@0 {
+			qcom,mode-h-active = <1920>;
+			qcom,mode-h-front-porch = <88>;
+			qcom,mode-h-pulse-width = <44>;
+			qcom,mode-h-back-porch = <148>;
+			qcom,mode-h-active-high;
+			qcom,mode-v-active = <1080>;
+			qcom,mode-v-front-porch = <4>;
+			qcom,mode-v-pulse-width = <5>;
+			qcom,mode-v-back-porch = <36>;
+			qcom,mode-v-active-high;
+			qcom,mode-refresh-rate = <60>;
+			qcom,mode-clock-in-khz = <148500>;
+		};
+
+		port@1 {
+			qcom,mode-h-active = <1920>;
+			qcom,mode-h-front-porch = <88>;
+			qcom,mode-h-pulse-width = <44>;
+			qcom,mode-h-back-porch = <148>;
+			qcom,mode-h-active-high;
+			qcom,mode-v-active = <1080>;
+			qcom,mode-v-front-porch = <4>;
+			qcom,mode-v-pulse-width = <5>;
+			qcom,mode-v-back-porch = <36>;
+			qcom,mode-v-active-high;
+			qcom,mode-refresh-rate = <60>;
+			qcom,mode-clock-in-khz = <148500>;
+		};
+	};
+};