LCD非设备树驱动框架参考:
https://blog.csdn.net/qq_34968572/article/details/89922596
一:设备树文件分析
1、公用文件imx6ull.dtsi
lcdif: lcdif@021c8000 {
compatible = "fsl,imx6ul-lcdif", "fsl,imx28-lcdif";
reg = <0x021c8000 0x4000>;
interrupts = <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clks IMX6UL_CLK_LCDIF_PIX>,
<&clks IMX6UL_CLK_LCDIF_APB>,
<&clks IMX6UL_CLK_DUMMY>;
clock-names = "pix", "axi", "disp_axi";
status = "disabled";
};
lcdif节点为imx6ull芯片的板子所共有的并不完整,像屏幕参数这些需要根据不同硬件平台去添加,分别有各自对应的dts文件。
根据lcdif节点compatible属性“fsl,imx6ul-lcdif", "fsl,imx28-lcdif”可以找到imx6ull的LCD驱动文件: drivers/video/fbdev/mxsfb.c
static const struct of_device_id mxsfb_dt_ids[] = {
{ .compatible = "fsl,imx23-lcdif", .data = &mxsfb_devtype[0], },
{ .compatible = "fsl,imx28-lcdif", .data = &mxsfb_devtype[1], },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mxsfb_dt_ids);
... ...
static struct platform_driver mxsfb_driver = {
.probe = mxsfb_probe,
.remove = mxsfb_remove,
.shutdown = mxsfb_shutdown,
.id_table = mxsfb_devtype,
.driver = {
.name = DRIVER_NAME,
.of_match_table = mxsfb_dt_ids,
.pm = &mxsfb_pm_ops,
},
};
2、LCD屏幕IO配置
pinctrl_lcdif_dat: lcdifdatgrp {
fsl,pins = <
MX6UL_PAD_LCD_DATA00__LCDIF_DATA00 0x79
MX6UL_PAD_LCD_DATA01__LCDIF_DATA01 0x79
MX6UL_PAD_LCD_DATA02__LCDIF_DATA02 0x79
MX6UL_PAD_LCD_DATA03__LCDIF_DATA03 0x79
MX6UL_PAD_LCD_DATA04__LCDIF_DATA04 0x79
MX6UL_PAD_LCD_DATA05__LCDIF_DATA05 0x79
MX6UL_PAD_LCD_DATA06__LCDIF_DATA06 0x79
MX6UL_PAD_LCD_DATA07__LCDIF_DATA07 0x79
MX6UL_PAD_LCD_DATA08__LCDIF_DATA08 0x79
MX6UL_PAD_LCD_DATA09__LCDIF_DATA09 0x79
MX6UL_PAD_LCD_DATA10__LCDIF_DATA10 0x79
MX6UL_PAD_LCD_DATA11__LCDIF_DATA11 0x79
MX6UL_PAD_LCD_DATA12__LCDIF_DATA12 0x79
MX6UL_PAD_LCD_DATA13__LCDIF_DATA13 0x79
MX6UL_PAD_LCD_DATA14__LCDIF_DATA14 0x79
MX6UL_PAD_LCD_DATA15__LCDIF_DATA15 0x79
MX6UL_PAD_LCD_DATA16__LCDIF_DATA16 0x79
MX6UL_PAD_LCD_DATA17__LCDIF_DATA17 0x79
MX6UL_PAD_LCD_DATA18__LCDIF_DATA18 0x79
MX6UL_PAD_LCD_DATA19__LCDIF_DATA19 0x79
MX6UL_PAD_LCD_DATA20__LCDIF_DATA20 0x79
MX6UL_PAD_LCD_DATA21__LCDIF_DATA21 0x79
MX6UL_PAD_LCD_DATA22__LCDIF_DATA22 0x79
MX6UL_PAD_LCD_DATA23__LCDIF_DATA23 0x79
>;
};
pinctrl_lcdif_ctrl: lcdifctrlgrp {
fsl,pins = <
MX6UL_PAD_LCD_CLK__LCDIF_CLK 0x79
MX6UL_PAD_LCD_ENABLE__LCDIF_ENABLE 0x79
MX6UL_PAD_LCD_HSYNC__LCDIF_HSYNC 0x79
MX6UL_PAD_LCD_VSYNC__LCDIF_VSYNC 0x79
>;
};
pinctrl_pwm1: pwm1grp {
fsl,pins = <
MX6UL_PAD_GPIO1_IO08__PWM1_OUT 0x110b0
>;
};
子节点pinctrl_lcdif_dat为RGBLCD的24根数据线配置项
子节点pinctrl_lcdif_ctrl为RBGLCD的4根控制线配置项包括CLK
子节点pinctrl_pwm1为LCD背光PWM引脚的配置项
3、LCD屏幕参数节点信息
&lcdif {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_lcdif_dat /* 使用到的 IO */
&pinctrl_lcdif_ctrl;
display = <&display0>;
status = "okay";
display0: display { /* LCD 属性信息 */
bits-per-pixel = <24>; /* 一个像素占用 24bit */
bus-width = <24>; /* 总线宽度 */
display-timings { /* 时序信息 */
native-mode = <&timing0>;
timing0: timing0 {
clock-frequency = <51200000>;
hactive = <1024>;
vactive = <600>;
hfront-porch = <160>;
hback-porch = <140>;
hsync-len = <20>;
vback-porch = <20>;
vfront-porch = <12>;
vsync-len = <3>;
hsync-active = <0>; /* hsync 数据线极性 */
vsync-active = <0>; /* vsync 数据线极性 */
de-active = <1>; /* de 数据线极性 */
pixelclk-active = <0>; /* clk 数据线先极性 */
};
};
};
};
4、LCD背光
(1)PWM驱动
pwm1: pwm@02080000 {
compatible = "fsl,imx6ul-pwm", "fsl,imx27-pwm";
reg = <0x02080000 0x4000>;
interrupts = <GIC_SPI 83 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clks IMX6UL_CLK_PWM1>,
<&clks IMX6UL_CLK_PWM1>;
clock-names = "ipg", "per";
#pwm-cells = <2>;
};
搜索compatible属性就可以找到linux内核中pwm的驱动
(2)pwm节点添加
在对应的开发板设备树dts文件下追加:
&pwm1 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_pwm1>;
status = "okay";
};
(3)连接背光节点到linux
backlight {
compatible = "pwm-backlight";
pwms = <&pwm1 0 5000000>;
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
status = "okay";
};
二:编译调试
1、开启Linux启动时的小企鹅logo
2、设置LCD作为终端控制台
(1)修改uboot的bootargs:打开两个console
setenv bootargs 'console=tty1 console=ttymxc0,115200 root=/dev/nfs rw nfsroot=192.168.1.250:
/home/zuozhongkai/linux/nfs/rootfs ip=192.168.1.251:192.168.1.250:192.168.1.1:255.255.255.0::eth0:
off'
(2)修改/etc/inittab
添加:
tty1::askfirst:-/bin/sh
启动后可输入 echo hello linux >/dev/tty1
3、调节背光
echo n > brightness
其中n为亮度级别最大为7