[Bug 93578] Intel HD 520 failed to train DP when connected with a external monitor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93578

--- Comment #4 from peter.wood at usask.ca ---
Just as an update which might help narrow down the problem.
After I upgraded Bios yesterday, VGA input from the USB-C adapter now shows up
as DP1.
I am also able to activate external monitor through VGA at 1920x1080.
Still no connection / system freeze if I try to connect via HDMI port.
My external monitor is a 4K monitor (native resolution 3400 x 2160). I think I
read somewhere that the adapter (DA200) only supports 2400x1200 ( a lower
resolution, anyway). I also read somewhere that the DRM training is implemented
so that it probes for higher resolutions first and then goes down. If the
Monitor reports that it is able to support a higher resolution than what the
adapter can actually support, this might cause the system to hang.
So, unless the code is altered, the only solution seems to be to use a USB-C
adapter/dock which is actually able to support the highest resolution the
external monitor can display.
My xrandr output with the external monitor connected via VGA(it shows as DP1):
Screen 0: minimum 8 x 8, current 3520 x 1080, maximum 32767 x 32767
eDP1 connected 1600x900+1920+0 (normal left inverted right x axis y axis) 294mm
x 165mm
   3200x1800     59.98*+  47.99
   2880x1620     60.00
   2560x1440     60.00
   2048x1536     60.00
   1920x1440     60.00
   1856x1392     60.01
   1792x1344     60.01
   2048x1152     60.00
   1920x1080     60.00
   1600x1200     60.00
   1400x1050     59.98
   1600x900      60.00
   1280x1024     60.02
   1280x960      60.00
   1368x768      60.00
   1280x720      60.00
   1024x768      60.00
   1024x576      60.00
   960x540       60.00
   800x600       60.32    56.25
   864x486       60.00
   640x480       59.94
   720x405       60.00
   640x360       60.00
DP1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 878mm x
485mm
   1920x1080     60.00*+
   1680x1050     59.95
   1280x1024     75.02    60.02
   1440x900      74.98    59.89
   1280x960      60.00
   1280x720      60.00
   1024x768      75.08    60.00
   800x600       75.00    60.32
   640x480       75.00    72.81    66.67    60.00
   720x400       70.08
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

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