[RK3288][Android6.0] 如何配置MIPI DSI Clock和PCLK

2019-11-09 15:42:41

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Platform: RK3288OS: Android 6.0Kernel: 3.10.92RK针对MipI DSI的lcd配置时有两个clock, rockchip,dsi_hs_clk 和 clock-frequency.文件中如下:disp_mipi_init: mipi_dsi_init{ compatible = "rockchip,mipi_dsi_init"; rockchip,screen_init = <1>; rockchip,dsi_lane = <4>; rockchip,dsi_hs_clk = <348>; rockchip,mipi_dsi_num = <1>;};disp_timings: display-timings { native-mode = <&timing0>; compatible = "rockchip,display-timings"; timing0: timing0 { screen-type = <SCREEN_MIPI>; lvds-format = <LVDS_8BIT_2>; out-face = <OUT_P888>; clock-frequency = <58200000>; hactive = <480>; vactive = <1280>; hback-porch = <160>; hfront-porch = <160>; vback-porch = <10>; vfront-porch = <12>; hsync-len = <24>; vsync-len = <2>; hsync-active = <0>; vsync-active = <0>; de-active = <0>; pixelclk-active = <0>; swap-rb = <0>; swap-rg = <0>; swap-gb = <0>; };};有人可能对这两个值不太清楚如何设置,而设置出错会引起显示异常,这里简要说明下:clock-frequency:即DCLK(dotc clock), PCLK(pixel clock).clock-frequency = (h_active + hfp + hbp + h_sync) * (v_active + vfp + vbp + v_sync) * fps厂商给的参考值是58.2MHz, 那么fps就是:fps = 58200000 / (480 + 160 + 160 +24) * (1280 + 12 + 10 + 2) = 54HzPCLK不能太大,Android支持不超过60fps.PCLK不能太小,小了画面刷新率会比较慢.rockchip,dsi_hs_clk:即每条MIPI data lane 传输速率.dsi_hs_clk = ((h_active + hfp + hbp + h_sync) * (v_active + vfp + vbp + v_sync) * fps * bpp) / lane_number这里就是:dsi_hs_clk = ((480 + 160 + 160 +24) * (1280 + 12 + 10 + 2) * 54 * 24) / 4 = 348136704 bps = 348 Mbpshs_clk不能太小,太小会显示灰屏,偏小会偏移.hs_clk不能太大,过大画面会显示条纹.

RK文档有提到 dsi_hs_clk还需要加上100, 追踪了下源码,没看出来.

另外我有实际测试其中一款屏,发现最终的值还是会有差异,不知道这是为什么.

顺便说下, 由于MIPI DSI上升沿和下降沿都可以发送数据,所以MIPI CLK Lane * 2 = MIPI DATA Lane在测量的时候, 要注意MIPI DSI CLK Lane的时钟速率会慢一倍.参考:http://blog.csdn.net/bmw7bmw7/article/details/45876487

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