DP MST with WD15 Dock leads to inconsistent port number
Assigned to Intel GFX Bugs mailing list
Created attachment 145815
dmesg with "drm.debug=0x1e log_buf_len=1M"
I am using a Dell Latitude 5491 with the WD15 dockr over USB type-C. The Dock is a DP MST Dock which 3 ports: HDMI, mDP and VGA. I am using HDMI and mDP. The displays work correctly, however, when I unplug and replug the displays, they get new names leading them to reset to the default display configuration until I also configure displays with that name.
Tested to be broken on 5.3.7 as well as 5.4-rc4.
Attached dmesg and xrandr.
- Booted up while connected to Dock. Displays show up as DP-2-1 (DP-4 in the kernel) and DP-5. DP-6 also shows up but is disconnected (this is probably the VGA work). The output of xrandr is in xrandr_before_verbose.txt
- Detached dock from system. (See "XXXXXXXXXXXXXX unplug" in dmesg)
- Replug dock to system. (See "XXXXXXXXXXXXXX replug" in demsg)
- DP-2-1 and DP-5 show as disconnected. Monitors show as DP-6 and DP-7 instead. DP-8 also shows up disconnected.
- End of log (See "XXXXXXXXXXXXXX done" in dmesg)
Expected behavior: Two monitors show up as DP-2-1 and DP-2-2 and remain that way consistently.
The first time I unplug/replug after boot, this happens without fail. However, the later times sometimes the display port name changes sometimes it doesn't.
Linux Distribution: Mint 19.2
**Attachment 145815**, "dmesg with "drm.debug=0x1e log_buf_len=1M"":