rockchip — display-timing dts配置

关键词：rockchip; display-timing;hfront-porch, hback-porch, hsync-len；vfront-porch, vback-porch, vsync-len；clock-frequency；hsync-active；vsync-active；  

rockchip — display-timing dts配置

1、display-timing 参数说明如下：

  +----------+-------------------------------------+----------+-------+
  |          |        ↑                            |          |       |
  |          |        |vback_porch                 |          |       |
  |          |        ↓                            |          |       |
  +----------#######################################----------+-------+
  |          #        ↑                            #          |       |
  |          #        |                            #          |       |
  |  hback   #        |                            #  hfront  | hsync |
  |   porch  #        |       hactive              #  porch   |  len  |
  |<-------->#<-------+--------------------------->#<-------->|<----->|
  |          #        |                            #          |       |
  |          #        |vactive                     #          |       |
  |          #        |                            #          |       |
  |          #        ↓                            #          |       |
  +----------#######################################----------+-------+
  |          |        ↑                            |          |       |
  |          |        |vfront_porch                |          |       |
  |          |        ↓                            |          |       |
  +----------+-------------------------------------+----------+-------+
  |          |        ↑                            |          |       |
  |          |        |vsync_len                   |          |       |
  |          |        ↓                            |          |       |
  +----------+-------------------------------------+----------+-------+

2、display-timing 节点属性值配置：

 - native-mode: The native mode for the display, in case multiple modes are
		provided. When omitted, assume the first node is the native.

3、timing 子节点属性值配置：

 - hactive, vactive: 显示器的分辨率；
 - hfront-porch, hback-porch, hsync-len: 配置水平display-timing参数，以像素为单位；
   vfront-porch, vback-porch, vsync-len: 配置垂直display-timing参数，以像素为单位；
 - clock-frequency: 配置显示时钟，以HZ为单位；
 - hsync-active: 配置 hsync 脉冲有效极性，low/high/ignored
 - vsync-active: 配置 vsync 脉冲有效极性，low/high/ignored
 - de-active: 配置 data-enable 脉冲有效极性 low/high/ignored
 - pixelclk-active: with
			- active high = drive pixel data on rising edge/
					sample data on falling edge
			- active low  = drive pixel data on falling edge/
					sample data on rising edge
			- ignored     = ignored
 - interlaced (bool): boolean to enable interlaced mode
 - doublescan (bool): boolean to enable doublescan mode
 - doubleclk (bool): boolean to enable doubleclock mode

All the optional properties that are not bool follow the following logic:
    <1>: high active
    <0>: low active
    omitted: not used on hardware

4、实例，display-timing可以配置不同的信号timing，通过使用native-mode来指定使用的timing子节点，比如：

正常的使用如下：

Example:

	display-timings {
		native-mode = <&timing0>;
		timing0: 1080p24 {
			/* 1920x1080p24 */
			clock-frequency = <52000000>;
			hactive = <1920>;
			vactive = <1080>;
			hfront-porch = <25>;
			hback-porch = <25>;
			hsync-len = <25>;
			vback-porch = <2>;
			vfront-porch = <2>;
			vsync-len = <2>;
			hsync-active = <1>;
		};
	};

如果要切换display-timing，可以再定义一个timing子节点，如下：

Example:

	timing1: timing {
		/* 1920x1080p24 */
		clock-frequency = <148500000>;
		hactive = <1920>;
		vactive = <1080>;
		hsync-len = <0 44 60>;
		hfront-porch = <80 88 95>;
		hback-porch = <100 148 160>;
		vfront-porch = <0 4 6>;
		vback-porch = <0 36 50>;
		vsync-len = <0 5 6>;
	};

然后，只要把native-mode改成<&timing1>即可，子节点timing1也说明了，参数 可以设置成最小值，推荐值，最大值；