我有一个显示设备通过 HDMI 电缆连接到计算机。显示器通常可以工作，但休眠后会出现故障（“无信号”）。为什么xrandr尽管我使用的是 HDMI 端口，但 DP-1 仍显示为已连接？
$ xrandr -display :0.0 -q
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
DP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 217mm x 136mm
1280x800 59.81 +
1920x1080 60.00* 50.00 59.94 30.00 25.00 24.00 29.97 23.98
1920x1080i 60.00 50.00 59.94
1280x720 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
720x576 50.00
720x480 60.00 59.94
640x480 75.00 72.81 66.67 60.00 59.94
720x400 70.08
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
$ DISPLAY=:0 xrandr --prop
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
DP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 217mm x 136mm
EDID:
00ffffffffffff004c2dff0b01000000
27180103806639780a0adf9a59529425
204b53bfee0081c00101010101010101
0101010101019e20009051201f304880
3600d9880000001c011d007251d01e20
6e285500d9880000001e000000fd0018
4b1a5111000a202020202020000000fc
0053796e634d61737465720a20200125
020326f14b841303120514101f202122
2309070783010000e2000fe305030166
030c00100080023a801871382d40582c
4500d9880000001e023a80d072382d40
102c4580d9880000001e011d8018711c
1620582c2500d9880000009e011d80d0
721c1620102c2580d9880000009e0000
0000000000000000000000000000001a
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
non-desktop: 0
range: (0, 1)
link-status: Good
supported: Good, Bad
1280x800 59.81 +
1920x1080 60.00* 50.00 59.94 30.00 25.00 24.00 29.97 23.98
1920x1080i 60.00 50.00 59.94
1280x720 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
720x576 50.00
720x480 60.00 59.94
640x480 75.00 72.81 66.67 60.00 59.94
720x400 70.08
DP-2 disconnected (normal left inverted right x axis y axis)
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
non-desktop: 0
range: (0, 1)
link-status: Good
supported: Good, Bad
HDMI-1 disconnected (normal left inverted right x axis y axis)
aspect ratio: Automatic
supported: Automatic, 4:3, 16:9
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
non-desktop: 0
range: (0, 1)
link-status: Good
supported: Good, Bad
操作系统：Ubuntu 18.04