屏配置指南

本章节将介绍 LCD 的配置方法。

屏配置方式有以下几种：

将以下屏参数写入 panel 驱动源码中

时序参数

/* Init the videomode parameter, dts will override the initial value. */
static struct videomode panel_vm = {
    .pixelclock = 130000000,
    .hactive = 1080,
    .hfront_porch = 160,
    .hback_porch = 160,
    .hsync_len = 40,
    .vactive = 1920,
    .vfront_porch = 10,
    .vback_porch = 20,
    .vsync_len = 8,
    .flags = DISPLAY_FLAGS_HSYNC_LOW | DISPLAY_FLAGS_VSYNC_LOW |
        DISPLAY_FLAGS_DE_HIGH | DISPLAY_FLAGS_PIXDATA_POSEDGE
};

屏接口参数

static int panel_bind(struct device *dev, struct device *master, void *data)
{
    ...
    dsi->format = DSI_FMT_RGB888;
    dsi->mode = DSI_MOD_VID_PULSE;
    dsi->lane_num = 4;
    ...
}

将屏参数写入到 board.dts 文件中。

panel_lvds {
    compatible = "artinchip,aic-general-lvds-panel";
    enable-gpios = <&gpio_a 4 GPIO_ACTIVE_HIGH>;
    data-mapping = "vesa-24";
    data-channel = "single-link1";
    status = "okay";

    port {
        panel_lvds_in: endpoint {
            remote-endpoint = <&lvds0_out>;
        };
    };

    display-timings {
        native-mode = <&timing0>;
        timing0: timing0 {
            clock-frequency = <130000000>;
            hactive = <1024>;
            vactive = <600>;
            hback-porch = <140>;
            hfront-porch = <160>;
            hsync-len = <20>;
            vback-porch = <20>;
            vfront-porch = <12>;
            vsync-len = <3>;
            de-active = <1>;
            pixelclk-active = <1>;
    };
};

注：

对于屏时序参数，只有当 board.dts 文件的 panel 结点没有设置 display-timings 子节点时，方式一才会生效。

屏配置步骤

屏配置需要以下操作：

为 LCD 适配一款 panel 驱动。
确保一条正确的数据通路。

具体配置步骤如下：

配置 panel 驱动
选择使用 Luban SDK 提供的 RGB/LVDS panel 驱动，详见 Panel 配置。编写一个 panel 驱动，详情可查看屏驱动说明。

数据通路

LCD 正常显示时，显示模块会形成一条完整的数据通道。

fb0 --> display engine  --> display interface  --> panel

数据通道的关系在 board.dts 中体现，以 LVDS 屏幕为例：

&fb0 {
    port {
        fb0_out: endpoint {
            remote-endpoint = <&de0_in>;
        };
    };
};

&de0 {
    status = "okay";
    port@0 {
        reg = <0>;
        de0_in: endpoint {
            remote-endpoint = <&fb0_out>;
        };
    };

    port@1 {
        reg = <1>;
        de0_out: endpoint {
            remote-endpoint = <&lvds0_in>;
        };
    };
};

&rgb0 {
    status = "disabled";
    port@0 {
        reg = <0>;
        rgb0_in: endpoint {
            remote-endpoint = <&rgb0_in>;
        };
    };

    port@1 {
        reg = <1>;
        rgb0_out: endpoint {
            remote-endpoint = <&panel_rgb_in>;
        };
    };
};

&lvds0 {
    status = "okay";
    port@0 {
        reg = <0>;
        lvds0_in: endpoint {
            remote-endpoint = <&de0_out>;
        };
    };

    port@1 {
        reg = <1>;
        lvds0_out: endpoint {
            remote-endpoint = <&panel_lvds_in>;
        };
    };
};

&dsi0 {
    status = "disabled";
    port@0 {
        reg = <0>;
        dsi0_in: endpoint {
            remote-endpoint = <&dsi0_in>;
        };
    };

    port@1 {
        reg = <1>;
        dsi0_out: endpoint {
            remote-endpoint = <&panel_dsi_in>;
        };
    };
};

在上述例子中，board.dts 通过 port 和 status 结点，配置了一条数据通道。

fb       |      de    |     |     lvds    |     panel
port  --> port0   port1 -->  port0   port1 -->  port

如果 board.dts 中没有正确配置一条数据通道，显示驱动无法完成初始化。