Arch Linux

jnhieber

Member

From: Germany

Registered: 2011-02-01

Posts: 23

Incorrect resolution in TTY

Hi,
I have a incorrect resolution in the TTY.
My system:
- Thinkpad T440s with Intel HD4400
- Lenovo Ultra dock

On my dock are 2 screens:
- Screen 1: 1920x1200 connected via DP
- Screen 2: 1920x1080 connected via DVI

The dock uses a DP MST hub/switch.

When i boot, in grub the resolution seems to be 1920x1080 on ever screen which is OK,
but when kernel (every release) boots, Screen 1 reports 1680x1050.

I do early load i915 in initramfs.
When i check cat /sys/class/drm/card0-DP-3/modes the desired resolution is there.
I tried setting the resolution with video=DP-3:1920x1200 but then both external screens stay off and
do not work.

Intel driver with a DP MST dock is a horrible experience.

Only thing i notice are DP linktraining errors, but there was never
a time/kernel without any errors from Intel driver with my dock.

$ dmesg | grep drm
[    0.696033] [drm] Initialized drm 1.1.0 20060810
[    0.708966] [drm] Memory usable by graphics device = 2048M
[    0.708973] fb: switching to inteldrmfb from EFI VGA
[    0.709114] [drm] Replacing VGA console driver
[    0.714431] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[    0.714434] [drm] Driver supports precise vblank timestamp query.
[    0.735286] [drm] Initialized i915 1.6.0 20151218 for 0000:00:02.0 on minor 0
[    0.772535] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to update link training
[    0.945652] fbcon: inteldrmfb (fb0) is primary device
[    2.456640] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
[122500.423531] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* failed to get link status
[122500.426284] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization
[122500.426990] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* uncleared fifo underrun on pipe A
[122500.427015] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun

Normally, the incorrect resolution would not bother me because I work not often in TTY,
but I want to use Sway with Wayland. Sway uses WLC seems not to be able to switch TTY resolution.

So I end up with 1920x1200 downscaled to 1680x1050 and then from the display upscaled to 1920x1200.
Looks terrible.

Last edited by jnhieber (2016-05-02 07:58:57)

sigils

Member

Registered: 2016-07-12

Posts: 9

Re: Incorrect resolution in TTY

I have this same problem with a Thinkpad T460p without a dock.

https://bbs.archlinux.org/viewtopic.php?id=119015

This thread here might help you but it's old and I'm finding some of the links to be broken. I'm about to try some of the solutions there. Please let me know if you have found a way.

Last edited by sigils (2016-07-15 12:14:56)