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Capture log by below command echo 0x10e | sudo tee /sys/module/drm/parameters/debug

1. Boot up the system with type-c to hdmi dongle(connect to external monitor)
2. Un-plug type-c dongle at second 205
3. plug type-c dongle at second 224, but the screen doesn't come back, it's blank
4. run xrandr --auto blindly at second 240, and then the external monitor works

Or

3. run xrandr --auto without any monitor is connected

4. plug type-c dongle and the external display works

(when the external display works)

u@u-Unidentified-System:~$ DISPLAY=:0 xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 509mm x 286mm
   1920x1080     60.00*+  50.00    59.94  
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1280x720      60.00    60.00    50.00    59.94  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  

(when external display doesn't work)

u@u-Unidentified-System:~$ DISPLAY=:0 xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
  1920x1080 (0x47) 148.500MHz +HSync +VSync
        h: width  1920 start 2008 end 2052 total 2200 skew    0 clock  67.50KHz
        v: height 1080 start 1084 end 1089 total 1125           clock  60.00Hz

dmesg.log