[KBL-R] DP link training failures lead to downgraded link parameters and resolution
@ribalda
Submitted by Ricardo Ribalda Delgado Assigned to Intel GFX Bugs mailing list
Link to original bug (#106223)
Description
Created attachment 139073
Screen detected as HD
Tested on Debian 4.15 and 4.16 (from experimental)
I have a secondary monitor connected via USB-C adapter to HDMI (detected as DP by xrandr). It can manage resolutions up to 2560x1440.
Most of the time, when the system is booted the resolution is detected
ok, but If I suspend the machine, or replug the screen, or alternate
to the text console, the resolution is "downgraded" to Full HD.
It is very anonying to reconect the cable up to 5 times to get the expected resolution when this happens.
I have added the paramter drm.debug=0x06 and I can see that when it is on Full HD there are only 2 lanes detected instead of 4.
The adapter is brand new (Xiaomi) and the cable should be of good
quality (ethernet capable and tested on other platform).
Attached you will find a trace at Full HD and 1440p
Attachment 139073, "Screen detected as HD":
HD