1.开发板直接命令行切换
这种方法仅限本次开机，重启设备知乎又会重新加载DTS，变回mipi输出
命令：

cd /sys/kernel/debug/dispdbg
echo disp0 > name; echo switch1 > command; echo 4 10 0 0 0x4 0x101 0 0 0 8 > param; echo 1 > start;

此时开发板会改成HDMI输出，使用命令cat colorbar可以进行测试是否切换成功了：

echo 1 > /sys/class/disp/disp/attr/colorbar 

详见D1在线文档：https://d1.docs.aw-ol.com/study/study_5connect/#hdmi

2.烧HDMI固件
烧写官方提供的HDMI输出固件，就会变成HDMI输出，每次开机都是
详见：https://d1.docs.aw-ol.com/source/3_getimg/
固件下载地址：https://www.aw-ol.com/downloads/resources/44

3.修改源码
如果想自己制作一个HDMI输出的固件，可以按照如下方法修改源码
（1）修改DTS文件，uboot的dts和内核的dts都要改

tina/device/config/chips/d1/configs/nezha$ git diff .
diff --git a/configs/nezha/linux-5.4/board.dts b/configs/nezha/linux-5.4/board.dts
index bfeed6c..1cef004 100755
--- a/configs/nezha/linux-5.4/board.dts
+++ b/configs/nezha/linux-5.4/board.dts
@@ -1128,30 +1128,25 @@ chn_cfg_mode     : Hardware DE channel allocation config. 0:single display with
        disp_init_enable         = <1>;
        disp_mode                = <0>;

-       screen0_output_type      = <1>;
-       screen0_output_mode      = <4>;
-
-       screen1_output_type      = <3>;
-       screen1_output_mode      = <10>;
-
-       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>;
+    screen0_output_type      = <3>;
+    screen0_output_mode      = <10>;
+
+    screen0_output_format    = <0>;
+    screen0_output_bits      = <0>;
+    screen0_output_eotf      = <4>;
+    screen0_output_cs        = <257>;
+    screen0_output_dvi_hdmi  = <2>;
+    screen0_output_range     = <2>;
+    screen0_output_scan      = <0>;
+    screen0_output_aspect_ratio = <8>;
+
+    screen1_output_type      = <1>;
+    screen1_output_mode      = <4>;
+
+    dev0_output_type         = <4>;
+    dev0_output_mode         = <10>;
        dev0_screen_id           = <0>;
-       dev0_do_hpd              = <0>;
-
-       dev1_output_type         = <4>;
-       dev1_output_mode         = <10>;
-       dev1_screen_id           = <1>;
-       dev1_do_hpd              = <1>;
+       dev0_do_hpd              = <1>;

        def_output_dev           = <0>;
        hdmi_mode_check          = <1>;
diff --git a/configs/nezha/uboot-board.dts b/configs/nezha/uboot-board.dts
old mode 100644
new mode 100755
index 793dec2..a5c99a2
--- a/configs/nezha/uboot-board.dts
+++ b/configs/nezha/uboot-board.dts
@@ -214,30 +214,25 @@
        disp_init_enable         = <1>;
        disp_mode                = <0>;

-       screen0_output_type      = <1>;
-       screen0_output_mode      = <4>;
-
-       screen1_output_type      = <3>;
-       screen1_output_mode      = <10>;
-
-       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>;
+    screen0_output_type      = <3>;
+    screen0_output_mode      = <10>;
+
+    screen0_output_format    = <0>;
+    screen0_output_bits      = <0>;
+    screen0_output_eotf      = <4>;
+    screen0_output_cs        = <257>;
+    screen0_output_dvi_hdmi  = <2>;
+    screen0_output_range     = <2>;
+    screen0_output_scan      = <0>;
+    screen0_output_aspect_ratio = <8>;
+
+    screen1_output_type      = <1>;
+    screen1_output_mode      = <4>;
+
+    dev0_output_type         = <4>;
+    dev0_output_mode         = <10>;
        dev0_screen_id           = <0>;
-       dev0_do_hpd              = <0>;
-
-       dev1_output_type         = <4>;
-       dev1_output_mode         = <10>;
-       dev1_screen_id           = <1>;
-       dev1_do_hpd              = <1>;
+       dev0_do_hpd              = <1>;

        def_output_dev           = <0>;
        hdmi_mode_check          = <1>;

（2）重新编译uboot
因为单独make编译的时候默认是不编译ubootd的，所以需要编译一下uboot

//进入uboot代码路径
cboot
//单独编译uboot，编完uboot文件会自动复制到方案下，不用管它
muboot
//重新编译打包
make -j64
pack

（3）改掉启动logo（可选）
sdk自带的启动logo是适配mipi屏幕的，在HDMI屏幕上显示会异常，所以建议改掉原SDK自带那个哪吒的启动logo，改成了linux小企鹅，大家可以把tina/device/config/chips/d1/configs/nezha/config 下面的bootlogo.bmp文件替换成下面这个文件：
bootlogo.7z

完成以上几步之后，插上HDMI并启动开发板，显示器上就会输出linux小企鹅的logo了