Arch Linux

eyenseo

Member

Registered: 2014-12-20

Posts: 7

[SOLVED] External monitor uses wrong output

Hello,

Today I rebooted because I messed up with xrandr and afterwards my external monitor uses DP2 instead of DP1.

My laptop has only one DisplayPort and if I boot without the monitor plugged in DP2 and DP3 are not shown. As soon as I plug the monitor in they appear in xrandr.

Also once I unplug the monitor the folders

/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-DP-2

and

/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-DP-3

disappear and

/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-DP-1

stays there.

Here is a tree with the linux kernel

/sys/devices/pci0000:00/0000:00:02.0/drm/card0/
├── card0-DP-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── i2c-7 -> ../../../i2c-7
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-DP-2
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-DP-3
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-eDP-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── i2c-6 -> ../../../i2c-6
│   ├── intel_backlight
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-HDMI-A-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-HDMI-A-2
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-VGA-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── dev
├── device -> ../../../0000:00:02.0
├── error
├── gt_cur_freq_mhz
├── gt_max_freq_mhz
├── gt_min_freq_mhz
├── gt_RP0_freq_mhz
├── gt_RP1_freq_mhz
├── gt_RPn_freq_mhz
├── l3_parity
├── power
│   ├── async
│   ├── autosuspend_delay_ms
│   ├── control
│   ├── rc6_enable
│   ├── rc6pp_residency_ms
│   ├── rc6p_residency_ms
│   ├── rc6_residency_ms
│   ├── runtime_active_kids
│   ├── runtime_active_time
│   ├── runtime_enabled
│   ├── runtime_status
│   ├── runtime_suspended_time
│   └── runtime_usage
├── subsystem -> ../../../../../class/drm
└── uevent

and a tee with the linux-lts kernel

/sys/devices/pci0000:00/0000:00:02.0/drm/card0/
├── card0-DP-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── i2c-7 -> ../../../i2c-7
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-eDP-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── i2c-6 -> ../../../i2c-6
│   ├── intel_backlight
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-HDMI-A-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-HDMI-A-2
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── card0-VGA-1
│   ├── device -> ../../card0
│   ├── dpms
│   ├── edid
│   ├── enabled
│   ├── modes
│   ├── power
│   ├── status
│   ├── subsystem -> ../../../../../../class/drm
│   └── uevent
├── dev
├── device -> ../../../0000:00:02.0
├── error
├── gt_cur_freq_mhz
├── gt_max_freq_mhz
├── gt_min_freq_mhz
├── gt_RP0_freq_mhz
├── gt_RP1_freq_mhz
├── gt_RPn_freq_mhz
├── l3_parity
├── power
│   ├── async
│   ├── autosuspend_delay_ms
│   ├── control
│   ├── rc6_enable
│   ├── rc6pp_residency_ms
│   ├── rc6p_residency_ms
│   ├── rc6_residency_ms
│   ├── runtime_active_kids
│   ├── runtime_active_time
│   ├── runtime_enabled
│   ├── runtime_status
│   ├── runtime_suspended_time
│   └── runtime_usage
├── subsystem -> ../../../../../class/drm
└── uevent

I tried the linux-lts kernel and with that kernel DP1 is used as expected. I know that it is not the fault of the kernel, as it was working before with the linux kernel, I guess it is a configuration file that got somehow messed up.

It would be nice if someone could tell me what I have to do to fix that behavior!

Thank you,
Eyenseo

Last edited by eyenseo (2014-12-22 10:24:14)

eyenseo

Member

Registered: 2014-12-20

Posts: 7

Re: [SOLVED] External monitor uses wrong output

New rule in my Arch linux book:
If you can't find something in the internet about the problem you have with Arch linux, it might be not Arch linux.

At 2am I remembered that I changed a setting in my external monitor (while rebooting ) to use DisplayPort 1.2 instead of 1.1 ... that's it.
But I still would like to know why arch linux doesn't "mount" the Monitor at DP1 and instead creates DP2 and DP3.

I'll mark it solved - have a nice Christmas time!