全志的方案目前应用的比较广泛，而且性价比高，很多人在入手全志android开发的时候会比较难入手，平板第一功能是什么？屏幕！下面给大家介绍一下在全志平台开发屏幕的全过程。
屏幕调试首先要拿到屏厂的屏幕参数，比如下面这个图片：
这些参数怎么用？看下面这些公式：
要调试屏幕，肯定会涉及到驱动开发和适配，驱动代码的添加必须在内核和uboot同时添加，否则会导致屏幕异常，对应的路径为：
内核路径：longan/kernel/linux-4.9/drivers/video/fbdev/sunxi/disp2/disp/lcd/
Uboot路径：longan/brandy/brandy-2.0/u-boot-2018/drivers/video/sunxi/disp2/disp/lcd/
设备树配置，主要配置disp、lcd0这两个节点：
disp: disp@06000000 {
disp_init_enable = <1>;
disp_mode = <0>;
screen0_output_type = <1>;
screen0_output_mode = <4>;
screen1_output_type = <1>;
screen1_output_mode = <4>;
screen1_output_format = <0>;
screen1_output_bits = <0>;
screen1_output_eotf = <4>;
screen1_output_cs = <257>;
screen1_output_dvi_hdmi = <2>;
screen1_output_range = <2>;
screen1_output_scan = <0>;
screen1_output_aspect_ratio = <8>;
dev0_output_type = <1>;
dev0_output_mode = <4>;
dev0_screen_id = <0>;
dev0_do_hpd = <0>;
dev1_output_type = <4>;
dev1_output_mode = <10>;
dev1_screen_id = <1>;
dev1_do_hpd = <1>;
def_output_dev = <0>;
hdmi_mode_check = <1>;
fb0_format = <0>;
fb0_width = <480>;
fb0_height = <800>;
fb1_format = <0>;
fb1_width = <0>;
fb1_height = <0>;
chn_cfg_mode = <1>;
disp_para_zone = <1>;
dc1sw-supply = <®_dc1sw>;
eldo3-supply = <®_eldo3>;
dcdc1-supply = <®_dcdc1>;
};
lcd0: lcd0@01c0c000 {
lcd_used = <1>;
lcd_driver_name = "mipi_gc9503v";
lcd_backlight = <50>;
lcd_if = <4>;
lcd_x = <480>;
lcd_y = <800>;
lcd_width = <117>;
lcd_height = <39>;
lcd_dclk_freq = <30>;
lcd_pwm_used = <1>;
lcd_pwm_ch = <3>;
lcd_pwm_freq = <50000>;
lcd_pwm_pol = <1>;
lcd_pwm_max_limit = <255>;
lcd_hbp = <60>;
lcd_ht = <580>;
lcd_hspw = <20>;
lcd_vbp = <38>;
lcd_vt = <858>;
lcd_vspw = <8>;
lcd_frm = <0>;
lcd_gamma_en = <0>;
lcd_bright_curve_en = <0>;
lcd_cmap_en = <0>;
deu_mode = <0>;
lcdgamma4iep = <22>;
smart_color = <90>;
lcd_dsi_if = <0>;
lcd_dsi_lane = <2>;
lcd_dsi_format = <0>;
lcd_dsi_te = <0>;
lcd_dsi_eotp = <0>;
lcd_pin_power = "dcdc1";
lcd_pin_power1 = "eldo3";
lcd_power = "dc1sw";
lcd_gpio_0 = <&r_pio PL 11 1 0 3 1>;
pinctrl-0 = <&dsi2lane_pins_a>;
pinctrl-1 = <&dsi2lane_pins_b>;
};
修改相关文件，因为硬件是两线制，所以需要添加dsi2lane_pins_a这个节点，引脚根据原理图添加就可以了，这里引脚都放到这个节点下，就是复用为摄像头功能：
longan/kernel/linux-4.9/arch/arm64/boot/dts/sunxi/sun50iw10p1-pinctrl.dtsi
dsi2lane_pins_a: dsi2lane@0 {
allwinner,pins = "PD0", "PD1", "PD2", "PD3","PD6", "PD7";
allwinner,pname = "PD0", "PD1", "PD2", "PD3","PD6", "PD7";
allwinner,function = "dsi2lane";
allwinner,muxsel = <4>;
allwinner,drive = <3>;
allwinner,pull = <0>;
};
dsi2lane_pins_b: dsi2lane@1 {
allwinner,pins = "PD0", "PD1", "PD2", "PD3","PD6", "PD7";
allwinner,pname = "PD0", "PD1", "PD2", "PD3","PD6", "PD7";
allwinner,function = "dsi2lane_suspend";
allwinner,muxsel = <7>;
allwinner,drive = <1>;
allwinner,pull = <0>;
};
longan/kernel/linux-4.9/drivers/video/fbdev/sunxi/disp2/disp/Makefile
longan/brandy/brandy-2.0/u-boot-2018/configs/sun50iw10p1_defconfig
CONFIG_LCD_SUPPORT_MIPI_GC9503V=y
longan/brandy/brandy-2.0/u-boot-2018/drivers/video/sunxi/disp2/disp/lcd/panels.h
extern __lcd_panel_t mipi_gc9503v_panel;
longan/brandy/brandy-2.0/u-boot-2018/drivers/video/sunxi/disp2/disp/Makefile
disp-y += lcd/mipi_gc9503v.o
longan/brandy/brandy-2.0/u-boot-2018/drivers/video/sunxi/disp2/disp/lcd/panels.c
&mipi_gc9503v_panel,
longan/kernel/linux-4.9/drivers/video/fbdev/sunxi/disp2/disp/lcd/panels.c
&mipi_gc9503v_panel,
longan/kernel/linux-4.9/drivers/video/fbdev/sunxi/disp2/disp/lcd/panels.h
extern struct __lcd_panel mipi_800x1280_panel;
前面这部分只是按照平台的要求去做了配置，更重要的是把驱动写好，如果驱动没写好也会出现各种问题，比如屏幕亮不起来。如果uboot中没有添加驱动，那么连背光都不亮。下面看驱动代码:
平常就给出了如下其他平台的操作代码，需要按照全志平台修改
全志平台修改代码如下，主要涵盖是修改这部分代码，当然数组的形式也改变了，细心的读者可以重点对比一下，避免踩坑：