LCD 使用

简介

Face-RK3399开发板支持MIPI屏幕，接口对应板子上的位置如下图：

MIPI屏

客户根据需要在自行添加mipi硬件接口之后，配置MIPI屏的 Timing dts文件，
在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-face-mipi8.dts中
可以看到以下语句：

   display-timings {
   		native-mode = <&timing0>;
   		timing0: timing0 {
   			clock-frequency = <67000000>;//<80000000>;
   			hactive = <800>;//<768>;
   			vactive = <1280>;
   			hsync-len = <20>;   //20, 50
   			hback-porch = <20>; //50, 56
   			hfront-porch = <32>;//50, 30
   			vsync-len = <4>;
   			vback-porch = <4>;
   			vfront-porch = <8>;
   			hsync-active = <0>;
   			vsync-active = <0>;
   			de-active = <0>;
   			pixelclk-active = <0>;
   		};
   	};
   };

Kernel 在kernel/drivers/gpu/drm/panel/panel-simple.c中可以看到在初始化
函数panel_simple_probe中初始化了获取时序的函数。

   static int panel_simple_probe(struct device *dev, const struct panel_desc *desc){
   ···
    panel->base.funcs = &panel_simple_funcs;
   ···
   }

该函数的在kernel/drivers/gpu/drm/panel/panel-simple.c中也有定义：

   static int panel_simple_get_timings(struct drm_panel *panel,unsigned int num_timings,struct display_timing *timings)
   {
       struct panel_simple *p = to_panel_simple(panel); 
       unsigned int i;
       if (!p->desc)  
           return 0;
           
       if (p->desc->num_timings < num_timings)  
           num_timings = p->desc->num_timings;
           
       if (timings)  
           for (i = 0; i < num_timings; i++)   
           timings[i] = p->desc->timings[i];
       return p->desc->num_timings;
   }

mipi屏上完电后需要发送初始化指令才能使之工作，可以在
kernel/arch/arm64/boot/dts/rockchip/firefly-face-mipi8.dts中可以看到
mipi的初始化指令列表：

   &mipi_dsi {    
               status = "okay";      
           ...
               panel-init-sequence = [                
                   05 20 01 29                
                   05 96 01 11 
                   ...           
               ];            
               
               panel-exit-sequence = [                
                   05 05 01 28                
                   05 78 01 10            
               ];
           ...
   };

命令格式以及说明可参考以下附件：

Rockchip DRM Panel Porting Guide.pdf

发送指令可以看到在kernel/drivers/gpu/drm/panel/panel-simple.c文件中的
操作：

   static int panel_simple_enable(struct drm_panel *panel)
   {
       struct panel_simple *p = to_panel_simple(panel);
       int err;
       if (p->enabled)
           return 0;
       DBG("enter\n");
       if (p->on_cmds) {
           err = panel_simple_dsi_send_cmds(p, p->on_cmds);
           if (err)
               dev_err(p->dev, "failed to send on cmds\n");
       }
       if (p->desc && p->desc->delay.enable) {
           DBG("p->desc->delay.enable=%d\n", p->desc->delay.enable);
           msleep(p->desc->delay.enable);
       }
       if (p->backlight) {
           DBG("open backlight\n");
           p->backlight->props.power = FB_BLANK_UNBLANK;
           backlight_update_status(p->backlight);
       }
       p->enabled = true;
       return 0;
   }

U-boot 发送指令可以看到在u-boot/drivers/video/rockchip-dw-mipi-dsi.c文
件中的操作：

   static int rockchip_dw_mipi_dsi_enable(struct display_state *state)
   {
       struct connector_state *conn_state = &state->conn_state;
       struct crtc_state *crtc_state = &state->crtc_state;
       const struct rockchip_connector *connector = conn_state->connector;
       const struct dw_mipi_dsi_plat_data *pdata = connector->data;
       struct dw_mipi_dsi *dsi = conn_state->private;
       u32 val;
       DBG("enter\n");
       dw_mipi_dsi_set_mode(dsi, DW_MIPI_DSI_VID_MODE);
       dsi_write(dsi, DSI_MODE_CFG, ENABLE_CMD_MODE);
       dw_mipi_dsi_set_mode(dsi, DW_MIPI_DSI_VID_MODE);
       if (!pdata->has_vop_sel)
           return 0;
       if (pdata->grf_switch_reg) {
           if (crtc_state->crtc_id)
               val = pdata->dsi0_en_bit | (pdata->dsi0_en_bit << 16);
           else
               val = pdata->dsi0_en_bit << 16;
           writel(val, RKIO_GRF_PHYS + pdata->grf_switch_reg);
       }
       debug("vop %s output to dsi0\n", (crtc_state->crtc_id) ? "LIT" : "BIG");
       //rockchip_dw_mipi_dsi_read_allregs(dsi);
       return 0;
   }

EDP屏

在V2 版本硬件中，Face-rk3399 支持EDP屏幕显示输出。具体接口参考

《接口定义》

章节部分图片。

客户根据需要在自行添加EDP硬件接口之后，配置EDP屏的 Timing dts文件，在
kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-face-edp15.dts中可
以看到以下语句：

   display-timings {
           native-mode = <&timing0>;
           timing0: timing0 {
                   clock-frequency = <140000000>;
                   hactive = <1920>;
                   vactive = <1080>;
                   hfront-porch = <100>;
                   hsync-len = <40>;
                   hback-porch = <40>;
                   vfront-porch = <10>;
                   vsync-len = <10>;
                   vback-porch = <10>;
                   hsync-active = <0>;
                   vsync-active = <0>;
                   de-active = <0>;
                   pixelclk-active = <0>;
           };                                                                                                                             
   };

这里定义了LCD的电源控制引脚：

lcd_en:gpios = <&gpio3 26 GPIO_ACTIVE_HIGH>;