Can't set max resolution on monitor with Displayport cable

altiris · 2015-02-18 20:51:27

I have an ASUS VG248QE and I could set the max resolution, which is 1920x1080, just fine on Cinnamon Display settings when using a Dual Link DVI cable. I put in a Mini display port to display port cable (one end is mini display other end is display port, the mini goes into the video card and the regular plugs into the monitor) just to see if it would work on Linux and everything works alright except the max resolution is 1024x768 instead of 1920x1080. The cable is fine as on windows 7 I can set it to max resolution.

So uh....what is this related to? I am using the xf86-video-ati driver so is this a bug with that or is it xorg related?

HarlemSquirrel · 2015-02-21 18:04:26

I am having a similar issue with my ASUS PB278 monitor that is supposed to run at 2560 x 1440 with my AMD R9 270X and the open source drivers. It works as expected with HDMI and everything worked fine through displayport with my R7 260X card before I upgraded.

I wrote a little script that is a temporary work around that I run at boot when I want to use the displayport. You will have to change "2560x1440_60.00" to "1920x1080_60.00" and "cvt 2560 1440" to "cvt 1920 1080" for your setup.

#!/bin/bash

cvt 2560 1440

xrandr --newmode "2560x1440_60.00"  312.25  2560 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync

xrandr --addmode DisplayPort-0 2560x1440_60.00

xrandr --output DisplayPort-0 --mode 2560x1440_60.00

notify-send "You should be all set at 1440p, buddy!"

There seems to be an issue reading the EDID via displayport with certain AMD graphics chips because I get this when running it:

$ sudo get-edid
This is read-edid version 3.0.1. Prepare for some fun.
Attempting to use i2c interface
Looks like no busses have an EDID. Sorry!
Attempting to use the classical VBE interface

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f00 bx=0x0 cx=0x0
	Function supported
	Call successful

	VBE version 300
	VBE string at 0xc0244 "AMD ATOMBIOS"

VBE/DDC service about to be called
	Report DDC capabilities

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f15 bx=0x0 cx=0x0
	Function supported
	Call successful

	Monitor and video card combination does not support DDC1 transfers
	Monitor and video card combination supports DDC2 transfers
	0 seconds per 128 byte EDID block transfer
	Screen is not blanked during DDC transfer

Reading next EDID block

VBE/DDC service about to be called
	Read EDID

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f15 bx=0x1 cx=0x0
	Function supported
	Call successful

i'e
           <"x:TO&
PT@qOV^)P0 5UP!E2LMTF003173
Lc@8<ASUS PB278
EDID claims 1 more blocks left


*********** Something special has happened!
This happens a lot with TV's, and other devices
with extension blocks. If you have a TV, don't bother.
Otherwise, please contact the author, Matthew Kern
E-mail: pyrophobicman@gmail.com
Please include full output from this program (especially that to stderr)



Reading next EDID block

VBE/DDC service about to be called
	Read EDID

	Performing real mode VBE call
	Interrupt 0x10 ax=0x4f15 bx=0x1 cx=0x0
	Function supported
	Call successful

  i'e
               <"x:TO&
PT@qOV^)P0 5UP!E2LMTF003173
Lc@8<ASUS PB278
EDID claims 1 more blocks left
EDID blocks left is wrong.
Your EDID is probably invalid.
  Looks like VBE was successful. Have a good day.

Last edited by HarlemSquirrel (2015-02-21 18:07:17)

Arch Linux

#1 2015-02-18 20:51:27

Can't set max resolution on monitor with Displayport cable

#2 2015-02-21 18:04:26

Re: Can't set max resolution on monitor with Displayport cable

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