Unable to change resolution

[mzuniga]

Opening arandr I see no other resolutions than current resolution (3840 x 2160). I want to lower the screen’s resolution. Does anyone know how I can do this?

[]$ xrandr --verbose
Screen 0: minimum 8 x 8, current 3840 x 2160, maximum 32767 x 32767
...
DP-2 connected primary 3840x2160+0+0 (0x1c1) normal (normal left inverted right x axis y axis) 381mm x 214mm
	Identifier: 0x1c0
	Timestamp:  36412
	Subpixel:   unknown
	Gamma:      1.3:1.3:1.4
	Brightness: 1.0
	Clones:    
	CRTC:       0
	CRTCs:      0 1 2 3
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	CTM: 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 
		0 1 
	CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0 
	Backlight: 34 
		range: (0, 100)
	EDID: 
		00ffffffffffff0006af9b3000000000
		001d0104a5261578039125a45435b626
		0e505400000001010101010101010101
		01010101010166d000a0f0703e803020
		35007dd61000001866d000a0f0706a82
		302035007dd610000018000000fe0041
		554f0a202020202020202020000000fe
		00423137335a414e30332e30200a00b6
	BorderDimensions: 4 
		supported: 4
	Border: 0 0 0 0 
		range: (0, 65535)
	SignalFormat: DisplayPort 
		supported: DisplayPort
	ConnectorType: Panel 
	ConnectorNumber: 3 
	_ConnectorLocation: 3 
	non-desktop: 0 
		supported: 0, 1
  3840x2160 (0x1c1) 533.500MHz -HSync -VSync *current +preferred
        h: width  3840 start 3888 end 3920 total 4000 skew    0 clock 133.38KHz
        v: height 2160 start 2163 end 2168 total 2222           clock  60.02Hz
  3840x2160 (0x1c2) 533.500MHz -HSync -VSync
        h: width  3840 start 3888 end 3920 total 4000 skew    0 clock 133.38KHz
        v: height 2160 start 2163 end 2168 total 2778           clock  48.01Hz

[mzuniga]

UPDATE:

Manually trying to add new resolution modes fail:

[]$ gtf 1920 1080 60

  # 1920x1080 @ 60.00 Hz (GTF) hsync: 67.08 kHz; pclk: 172.80 MHz
  Modeline "1920x1080_60.00"  172.80  1920 2040 2248 2576  1080 1081 1084 1118  -HSync +Vsync

[]$ xrandr --newmode "1920x1080_60.00"  172.80  1920 2040 2248 2576  1080 108
[]$ xrandr --addmode DP-2 "1920x1080_60.00"
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  43
  Current serial number in output stream:  44
[$ cvt 1920 1080 60
# 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
[]$ xrandr --newmode "1920x1080_60" 173.00  1920 2048 2248 2576  1080 1083 10
[]$ xrandr --addmode DP-2 "1920x1080_60"
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  43
  Current serial number in output stream:  44

However, I realised that I could change resolution directly, using:

[]$ xrandr -s 1920x1080

Source:
https://unix.stackexchange.com/questions/227876/how-to-set-custom-resolution-using-xrandr-when-the-resolution-is-not-available-i

[mzuniga]

No idea why different resolutions did not show up in arandr, nor why I wasn’t able to use xrandr to add new modes. However, using xrandr I’m able to change resolution so my problem is solved.

$ xrandr -s 1920x1080
$ xrandr -s 2560x1440
$ xrandr -s 3840x2160