[SOLVED] Rotation & refresh rate for ultra high resolution display

karkhaz · 2014-05-20 13:38:10

I am having trouble getting xrandr to recognise the mode for my new UHD display---a Dell UltraSharp UP2414Q. I would like the display to output at 2160x3840 at 60Hz (i.e. in portrait).

In summary, either it allows me to output at 3840x2160 but only at 30Hz---which is slow and laggy---or at 1440x576 at 50Hz. In either case, I cannot rotate the monitor to portrait mode by using xrandr --rotate right (issuing that command has no effect).

Has anybody else had similar troubles? I managed to find only this topic on the forum, but I don't think it's related.

Here are some more details:

In order to support my desired mode (both UHD and 60Hz refresh rate), DisplayPort 1.2 is required. My graphics card (Asus Radeon HD7970 DirectCU-II) does support DisplayPort 1.2. The monitor itself also (supposedly) supports 1.2, but this is where it gets weird.
The monitor has a DP 1.2 mode, and a legacy 1.1 mode. In 1.1 mode, it supports 3840x2160 at only 30Hz---fair enough, and that is what xrandr reports:
```
DisplayPort-1 connected 3840x2160+0+1024 (normal left inverted right x axis y axis) 527mm x 296mm
   3840x2160     29.98*+  30.30  
   1920x1200     59.88
     ... other, lower resolutions ...
```
But in 1.2 mode, which supposedly supports 3840x2160 at 60Hz, xrandr does not report the correct resolution at all:
```
DisplayPort-1 connected 1440x576+0+1024 (normal left inverted right x axis y axis) 527mm x 296mm
   1440x576i     50.00* 
   1024x768      60.00
      ... other, lower resolutions ...
```
these modes are way lower than what xrandr should be reporting.

I then tried to add a new mode to the monitor while it was in DP 1.2 mode, using the following steps:

$ cvt 3840 2160 60
Modeline "3840x2160_60.00"  712.75  3840 4160 4576 5312  2160 2163 2168 2237 -hsync +vsync
$ xrandr --newmode "mymode" 712.75  3840 4160 4576 5312  2160 2163 2168 2237 -hsync +vsync
$ xrandr --addmode DisplayPort-1 mymode
$ xrandr
DisplayPort-1 connected 3840x2160+0+1024 (normal left inverted right x axis y axis) 527mm x 296mm
   1440x576i     50.00  
    ... other modes ...
   mymode        59.98
$ xrandr --output DisplayPort-1 --mode mymode

As soon as I tried to change the mode to mymode with that last command, the screen turned off.

Attempting to rotate the monitor (xrandr --output DisplayPort-1 --rotate right) results in bizarre effects. Sometimes it simply doesn't work. Other times, the cursor moves across the screen as if the screen had been rotated, but the windows have not been rotated.

edit: Using the free radeon driver for my graphics board.

Last edited by karkhaz (2014-06-02 00:18:02)

karkhaz · 2014-06-02 00:17:47

Marking as solved and updating the wiki. The inability to rotate is due to acceleration being disabled when I use EXA rather than Glamour.

Using this option:

Section "Device"
  Option "AccelMethod" "EXA"
EndSection

in my xorg.conf.d/20-radeon.conf causes this error to appear when I issue the xrandr rotate command:

(EE) RADEON(0): Rotation requires acceleration!

Removing that option enables Glamor and I can rotate. However, I'm sticking with EXA due to Glamor's unusable 2D performace, as detailed in this section of the wiki.

Sources: this thread and comment 17 on that bug report.

Arch Linux

#1 2014-05-20 13:38:10

[SOLVED] Rotation & refresh rate for ultra high resolution display

#2 2014-06-02 00:17:47

Re: [SOLVED] Rotation & refresh rate for ultra high resolution display

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