Display looses resolution in Ubuntu 20.04.3 LTS if monitor switch is not connected to another pc

antogeo

6/2/23, 9:36 PM

I have a fresh installation of Ubuntu 20.04.3 LTS in a desktop which shares the screen with my laptop via a monitor switch. I have a set a custom resolution using

cvt 1680 1050
# 1680x1050 59.95 Hz (CVT 1.76MA) hsync: 65.29 kHz; pclk: 146.25 MHz
Modeline "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync
xrandr --listactivemonitors 
    Monitors: 1
     0: +*DisplayPort-0 1024/271x768/203+0+0  DisplayPort-0

and then:

xrandr --addmode DisplayPort-0 '1680x1050_60.00'
xrandr --newmode "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync

The problem starts if the HDMI cable of the laptop is disconnected from the monitor switch. Then resolution changes to the default 1024x768. It still works fine if the laptop is connected but switched of... I tried lots of things but in the end I only managed to mess up everything and I reinstalled Ubuntu.

some further info:

sudo lshw -c display

[sudo] password for antogeo: 
  *-display                 
       description: VGA compatible controller
       product: Bonaire [FirePro W5100]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:02:00.0
       version: 00
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=radeon latency=0
       resources: irq:39 memory:e0000000-efffffff memory:f0000000-f07fffff ioport:e000(size=256) memory:fbe00000-fbe3ffff memory:c0000-dffff

Thanks in advance for any help!

0 + 0

monitor

displayport

display-resolution

amd-graphics

20.04

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Display looses resolution in Ubuntu 20.04.3 LTS if monitor switch is not connected to another pc

TH: จอแสดงผลสูญเสียความละเอียดใน Ubuntu 20.04.3 LTS หากสวิตช์มอนิเตอร์ไม่ได้เชื่อมต่อกับพีซีเครื่องอื่น

RO: Afișajul pierde rezoluția în Ubuntu 20.04.3 LTS dacă comutatorul monitorului nu este conectat la un alt computer

RU: Дисплей теряет разрешение в Ubuntu 20.04.3 LTS, если переключатель монитора не подключен к другому компьютеру

VI: Màn hình mất độ phân giải trong Ubuntu 20.04.3 LTS nếu công tắc màn hình không được kết nối với máy tính khác

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