Mdthbs

I recently built a computer and put a fresh install of Debian 9 on it. However when I plug both monitors into the Radeon RX 550 graphics card, my desktop is mirrored instead of extended. On top of this I have been unable to change the default size of 1024x768 to the actual monitor resolution of 1600x900. Running xrandr I get

xrandr: Failed to get size of gamma for output default

Screen0: minimum 1024 x 768, curent 1024 x 768, maximum 1024 x 768

default connected primary 1024x768+0+0 0mm x 0mm

   1024x768      76.00*

One monitor is plugged into the DVI port and the other is plugged into the HDMI port.

This problem persists on both i3wm and XFCE, though currently I'm using i3wm

The package "firmware-amd-graphics" is installed.

My X logs https://gist.github.com/anonymous/fc1bb91a4778c5a43efca4a854efb164

More recent X logs https://gist.github.com/anonymous/cb6a1f2f2f7d901245d5b8869cbad25c
My xorg.conf https://gist.github.com/anonymous/6864f488ae8837966cfa3fffde059385

dmesg https://gist.github.com/anonymous/8fa180a9330adf674c39b949adaa00aa

I've had this issue as well in various Linux distros and have created a script that I copy to systems in which I encounter this problem, which I'll include below after a brief explanation of my findings, though I still have a problem with permanency as not all config files are created equal, or even present in some Linux OS flavors; however, I find that both utilities to query and set the modes are present ('cvt' and 'xrandr').

First of all you need to determine the parameters to set with 'xrandr' which you'll do with 'cvt' by executing the following in a terminal window. First, get the data from 'xrandr' as you already have. When I execute 'xrandr' it returns the following:

xrandr

Screen0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
1024x768 76.00*

The only info you really need from that block above is the device name, Screen0 which I'll put in the code below for your benefit. Make sure to change any data you get from xrandr and cvt that differs from my results as your hardware is different and may return different parameters.

You'll need to get your data from cvt doing:

cvt 1600 900

This should return something like:

# 1600x900 59.95 Hz (CVT 1.44M9) hsync: 55.99 kHz; pclk: 118.25 MHz
Modeline "1600x900_60.00" 118.25 1600 1696 1856 2112 900 903 908 934 -hsync +vsync

You'll need the Modeline data from the quotation mark through to the end of 'vsync'

With that, if I were doing it with that resolution and the hardware I have, I'd put the following into a script, save it as something like 'fixmyres.sh'

# Resolution fix for 1600x900 - changes to 1600x900 with cvt calculation



xrandr --newmode "1600x900_60.00"  118.25  1600 1696 1856 2112  900 903 908 934 -hsync +vsync

xrandr --addmode Screen0 1600x900_60.00

xrandr --output Screen0 --mode 1600x900_60.00

and set it as executable:

chmod a+x fixmyres.sh

then run it

./fixmyres.sh

I place the file on the desktop since the results have been inconsistent for me using the Xorg file(s).

I hope this helps. I'm still fairly wet behind the ears in my experience with Linux, but I had great difficulty finding this information and hope to save some legwork for others who are experiencing these problems as well. Now if I could only make it permanent with some Linux distros (I use Ubuntu, Fedora, Gentoo, BSD, and others, which are all different).

Happy computing!