linux设备树-LCD驱动程序

Posted 2023-05-04 大奥特曼打小怪兽

一、修改设备树

1.1 硬件接线

1.2 修改s3c2440-pinctrl.dtsi

修改内核arch/arm/boot/dts/s3c2440-pinctrl.dtsi文件，在pinctrl节点下添加两个引脚配置节点：

lcd_pinctrl: lcd_pinctrl 
    samsung,pins = "gpc-8", "gpc-9", "gpc-10", "gpc-11", "gpc-12", "gpc-13", "gpc-14", "gpc-15",
            "gpd-0", "gpd-1", "gpd-2", "gpd-3", "gpd-4", "gpd-5", "gpd-6", "gpd-7",
            "gpd-8", "gpd-9", "gpd-10", "gpd-11", "gpd-12", "gpd-13", "gpd-14", "gpd-15",
            "gpc-1", "gpc-2", "gpc-3", "gpc-4";
    samsung,pin-function = <EXYNOS_PIN_FUNC_2>;
;

lcd_backlight: lcd_backlight 
    samsung,pins = "gpg-4";
    samsung,pin-function = <3>;
;

lcd_pinctrl：配置GPC8、GPC9、GPC10等引脚功能为LCD。

lcd_backlight：配置GPG4引脚功能为LCD电源。

1.3 修改s3c2440-smdk2440.dts

在内核arch/arm/boot/dts/s3c2440-smdk2440.dts文件中添加fb0设备节点：

fb0: fb@4d000000
    compatible = "tq2440,lcd";
    reg = <0x4D000000 0x60>;
    interrupts = <0 0 16 3>;
    clocks = <&clocks HCLK_LCD>;
    clock-names = "lcd";
    pinctrl-names = "default";
    pinctrl-0 = <&lcd_pinctrl &lcd_backlight>;
    status = "okay";

    lcdcon5 = <0xb09>;
    type = <0x60>;
    width = /bits/ 16 <480>;
    height = /bits/ 16 <272>;
    pixclock = <100000>;
    xres = /bits/ 16 <480>;
    yres = /bits/ 16 <272>;
    bpp = /bits/ 16 <16>;
    left_margin = /bits/ 16 <2>;
    right_margin =/bits/ 16  <2>;
    hsync_len = /bits/ 16 <41>;
    upper_margin = /bits/ 16 <2>;
    lower_margin = /bits/ 16 <2>;
    vsync_len = /bits/ 16 <10>;
;

当platform设备和驱动匹配，就会调用pinctrl_bind_pins函数，该函数通过调用pinctrl_lookup_state函数获取状态名为default和init的状态，并分别保存到default_state和init_state成员变量中。如果找不到init状态，则选择default状态作为设备引脚的状态。

二、修改驱动程序

 

参考文章

[1]linux驱动移植-LCD驱动基础

[2]linux驱动移植-LCD设备驱动

[3]linux驱动移植-LCD触摸屏设备驱动

[4]第六课:在LCD驱动中使用设备树

[5]基于设备树的TQ2440触摸屏驱动移植

[6]tq2440_dt/drivers/video/fbdev/s3c2410fb.c

[7] tq2440_dt/arch/arm/boot/dts/s3c2440-tq2440-dt.dts

[8]tq2440_dt/arch/arm/boot/dts/s3c2440-pinctrl.dtsi

[9]Mini2440裸机开发之LCD基础

[10]Mini2440裸机开发之LCD编程（GB2312、ASCII字库制作）

Linux MIPI DSI驱动调试笔记-设备树DCS格式序列之配置LCD初始化代码

1、MIPI LCD初始化序列描述

在上一篇文章中，我们看到荣品的屏设备树中有这么一段代码，但是里面的数据是什么含义呢？

panel-init-sequence = [
   05 78 01 11
   05 78 01 29
  ];

今天来详细记录下我学习在设备树中适配MIPI-DSI LCD初始化代码的详细过程。Linux提供了配置初始化代码的接口，相应的设备树也就支持了,这部分在内核的文档里有写：

kernel/Documentation/devicetree/bindings/display/panel/simple-panel.txt

这个文档里简单描述了一下：

- panel-init-sequence:
- panel-exit-sequence:
 A byte stream formed by simple multiple dcs packets.
  byte 0: dcs data type
  byte 1: wait number of specified ms after dcs command transmitted
  byte 2: packet payload length
  byte 3 and beyond: number byte of payload

翻译过来大概的意思是：