Rk 平台显示屏调试

显示时序

首先需要了解这几个参数，并从显示屏的规格书找到这些值。

时序概述
名称	解释	缩写	单位
Clock Frequency	像素时钟	cf	hz
Horizontal Back Porch	水平后肩，水平同步信号之后的时延	hbp	clk
Horizontal Front Porch	水平前肩，水平同步信号之前的时延	hfp	clk
Horizontal Pulse Width	水平同步信号的长度	hsync	clk
Vertical Back Porch	垂直后肩，垂直同步信号之后的时延	vbp	line
Vertical Front Porch	垂直前肩，垂直同步信号之前的时延	vfp	line
Vertical Pulse Width	垂直同步信号长度	vsync	line

这里clk = 1 / cf，line =（hbp + hfp + hsync）* clk，假如显示屏的像素时钟规定为65000000hz，则clk = 1 / 65000000s

屏幕datasheet

Rk 平台显示屏调试

Main clock = clock-frequency = 72300000hz
Hor Blanking = hbp + hfb + hsync = 160
H Sync Pulse Width = hsync = 32
H Sync Offset = hbp = 48
所以 hfp = 160 - 32 - 48 = 80
Ver Blanking = vbp + vfp + vsync = 22
V Sync Pulse Width = vsync = 6
V Sync Offset = vbp = 3
所以vfp = 22 - 6 - 3 = 13

所以对应dts

#if 1
&edp {
   //vcc-supply = <&vdd10_lcd>;
   //vccio-supply = <&vcc18_lcd>;
   status = "okay";
};

&edp_phy {
status = "okay";
};

&edp {
status = "okay";
};

&edp_phy {
   status = "okay";
};
&route_edp {
   status = "okay";
};
&edp_in_vopb {
   status = "okay";
};
&edp_in_vopl {
   status = "disabled";
};

&edp_panel {
   compatible ="lg,lp079qx1-sp0v", "simple-panel";
   backlight = <&backlight>;
   enable-gpios = <&gpio7 14 GPIO_ACTIVE_HIGH>;

   enable-delay-ms = <120>;
   pinctrl-0 = <&lcd_cs>;
   power-supply = <&vcc_lcd>;
   status = "okay";

display_timings: display-timings {
native-mode = <&timing_edp>;

       timing_edp: timing0 {
           clock-frequency = <72300000>;
           hactive = <1366>;
           vactive = <768>;

           hfront-porch = <80>; //H blanking 160
           hsync-len = <32>;
           hback-porch = <48>;

           vfront-porch = <13>; //V blanking 22
           vsync-len = <6>;
           vback-porch = <3>;

           hsync-active = <0>;
           vsync-active = <0>;
           de-active = <0>;
           pixelclk-active = <0>;
       };
   };
};
#endif

&hdmi{
status = "disabled";
};

有的datasheet 会直接给出屏参如下图

Rk 平台显示屏调试

可以看到，此款 LCD 可以用 DE 和 SYNC 两种模式去驱动，我们常用的是 SYNC 模式，
从软件上来说， DE 模式和 SYNC 模式是一样的，软件上不做区分。从表中我们可以得
到如下参数：
Left_margin = HBP（Horizontal Back Porch） = 16;
Right_margin = HFP（Horizontal Front Porch） = 210;
Hsync = HPW（Horizontal Pulse Width ） = 30;
Xres = HVD(Horizontal Valid) = 800;
Upper_margin = VBP（Vertical Back Porch） = 10;
low_margin = VFP（Vertical Front Porch） = 22;
Vsync = VPW（Vertical Pulse Width） = 13;
Yres = VVD（Vertical Valid） = 480;
而且这些参数满足如下公式：
Left_margin + right_margin + hsync + xres = horizontal period
Upper_margin + low_margin + vsync + yres = vertical period

Rk 平台显示屏调试

显示时序

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