Arch Linux

Renfield

Member

Registered: 2017-11-07

Posts: 9

[Solved] Cannot set monitor resolution to 2560x1600

After an upgrade, I am no longer able to set my monitor's proper resolution, and I'm stuck at 1280x800. When I attempt this via xrandr, I get:

4> xrandr --newmode "2560x1600" 268.00  2560 2608 2640 2720  1600 1603 1609 1646 +hsync -vsync
5> xrandr --addmode DVI-D-0 "2560x1600"
6> xrandr --output DVI-D-0 --mode "2560x1600" --verbose
screen 0: 2560x1600 675x422 mm  96.30dpi
crtc 0:    2560x1600  59.86 +0+0 "DVI-D-0"
xrandr: Configure crtc 0 failed
crtc 0: disable
crtc 1: disable
crtc 2: disable
crtc 3: disable
crtc 4: disable
crtc 5: disable
screen 0: revert
crtc 0: revert
crtc 1: revert
crtc 2: revert
crtc 3: revert
crtc 4: revert
crtc 5: revert

This had been working for years. I have an AMD Radeon RX480. I was using the amdgpu-pro drivers, but while attempting to fix this, I have changed over to the amdgpu drivers.

I've never had to set the mode line or anything before. I believe that mode line is correct, as this output is in Xorg.0.log:

[    11.339] (II) AMDGPU(0): Printing DDC gathered Modelines:
[    11.339] (II) AMDGPU(0): Modeline "2560x1600"x0.0  268.00  2560 2608 2640 2720  1600 1603 1609 1646 +hsync -vsync (98.5 kHz eP)
[    11.339] (II) AMDGPU(0): Modeline "1280x800"x0.0   71.00  1280 1328 1360 1440  800 803 809 823 +hsync -vsync (49.3 kHz e)

Here's some more info:

12> uname -r
4.15.10-1-ARCH
13> lsmod | grep amdgpu
amdgpu               3104768  5
chash                  16384  1 amdgpu
i2c_algo_bit           16384  1 amdgpu
ttm                   118784  1 amdgpu
drm_kms_helper        200704  1 amdgpu
drm                   466944  6 amdgpu,ttm,drm_kms_helper
14> cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-linux root=UUID=4f8b36f7-70f4-40f5-b1b4-6d0a319bfe81 rw quiet
15> cat /sys/module/amdgpu/parameters/dc
-1

For that last one, somewhere I saw that maybe I need to turn off dc for the amdgpu module. So, I have this:

16> cat /etc/modprobe.d/20-amdgpu.conf 
options amdgpu amdgpu.dc=0

And I've also tried updating the initramfs in case it wasn't reading that file, but no matter what, it always shows up as -1.

23> pacman -Qi mesa lib32-mesa xf86-video-amdgpu | grep "Name\|Version"
Name            : mesa
Version         : 17.3.6-1
Name            : lib32-mesa
Version         : 17.3.6-1
Name            : xf86-video-amdgpu
Version         : 18.0.1-1

I'm not sure what to do now to get the full resolution working again.

Last edited by Renfield (2018-03-19 23:28:04)

Renfield

Member

Registered: 2017-11-07

Posts: 9

Re: [Solved] Cannot set monitor resolution to 2560x1600

I'd like to add that both grub and the initial console are at full resolution. It's just Xorg that will not display at the correct resolution.

Here is my Xorg configuration:

2> cat /etc/X11/xorg.conf.d/20-amdgpu.conf 
Section "Device"
	Identifier "AMD"
	Driver "amdgpu"
#	Option "TearFree" "true"
#	Option "DRI" "3"
EndSection

Section "Screen"
	Identifier "Screen 0"
	Device "AMD"
EndSection

Last edited by Renfield (2018-03-19 23:07:51)

loqs

Member

Registered: 2014-03-06

Posts: 17,372

Re: [Solved] Cannot set monitor resolution to 2560x1600

options amdgpu amdgpu.dc=0

Kernel_modules#Using_files_in_.2Fetc.2Fmodprobe.d.2F
The for mat is

options module_name parameter_name=parameter_value

amdgpu.dc should be just dc
Please use code tags for commands and their output.

Renfield

Member

Registered: 2017-11-07

Posts: 9

Re: [Solved] Cannot set monitor resolution to 2560x1600

Thank you, that worked. Then I had to go into the "Display" setting of XFCE because after fixing this and rebooting, although the login window was high resolution XFCE was still resetting to the lower resolution.