Arch Linux

jg-you

Member

Registered: 2018-07-05

Posts: 4

Set refresh rate for 4K monitor, optimal rate not showing in xrandr

Hi all,

I've just installed archlinux on my HP EliteBook Folio 1040 laptop.

I have a USB-C dock and a screen that both support 4K at 60hz (HP SB Elite USB-C G3 Dock and HP eliteDisplay S270n).
However, the default Xorg setup defaults to 4K at 30hz when I plug the dock, and it will not allow me to set a refresh rate of 60Hz.

I've followed the guide at https://wiki.archlinux.org/index.php/Xr … esolutions
to manually force the monitor to run at 60hz, but to no avail. I've looked through a few Newbie's corner thread and have not found anything.

The relevant part of the output of xrandr --props is

DP-1-2-2 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
    EDID: 
        00ffffffffffff00220e2f3501010101
        0c1c0104b53c22783a2895a7554ea326
        0f5054a10800d1c081c081809500a9c0
        a940b300d1004dd000a0f0703e803020
        350055502100001a000000fd00183c1b
        873c010a202020202020000000fc0048
        5020533237306e0a20202020000000ff
        0036434d383132304c53370a2020018f
        020310b14b6160101f04130312021101
        565e00a0a0a029503020350055502100
        001a04740030f2705a80b0588a005550
        2100001eef5100a0f070198030203500
        55502100001a00000000000000000000
        00000000000000000000000000000000
        00000000000000000000000000000000
        000000000000000000000000000000b5
    non-desktop: 0 
        supported: 0, 1
   3840x2160     30.00*   29.97    24.00  
   2560x1440     59.95  

As you can see, 60Hz is not even listed as an option for 4K.
Trying to add it with xrandr yields:

jgyou:~$> cvt -r 3840 2160 
# 3840x2160 59.97 Hz (CVT 8.29M9-R) hsync: 133.25 kHz; pclk: 533.00 MHz
Modeline "3840x2160R"  533.00  3840 3888 3920 4000  2160 2163 2168 2222 +hsync -vsync
jgyou:~$> xrandr --newmode  "3840x2160R"  533.00  3840 3888 3920 4000  2160 2163 2168 2222 +hsync -vsync
jgyou:~$> xrandr --addmode DP-1-2-2 3840x2160R
jgyou:~$> xrandr --output DP-1-2-2 --mode 3840x2160R
xrandr: Configure crtc 0 failed

Ẁhat should I do at this point?

Last edited by jg-you (2018-07-05 20:39:42)

radiomike

Member

Registered: 2013-12-19

Posts: 75

Re: Set refresh rate for 4K monitor, optimal rate not showing in xrandr

In order to get 4k at this refresh rate, displayport alt mode needs to be supported by your laptop. Probably simplest test is try it in windows. If it doesn't work at this res and refresh rate then you're either out of luck or using the wrong kind of usb-c cable.

If it does work, then you're probably in for a wait as there's no support for displayport alt mode in the kernel yet. If we're lucky it might appear in 4.19, but there are patches available in the kernel mailing list if you are feeling adventurous.

jg-you

Member

Registered: 2018-07-05

Posts: 4

Re: Set refresh rate for 4K monitor, optimal rate not showing in xrandr

Hu ho, impossible to make it work on Windows 10 either. Well though luck I guess.