kern/54615: genfb issues after switching graphics mode in efiboot

[martin%NetBSD.org@localhost]

>Number:         54615
>Category:       kern
>Synopsis:       genfb issues after switching graphics mode in efiboot
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Oct 12 14:30:01 +0000 2019
>Originator:     Martin Husemann
>Release:        NetBSD 9.99.15
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD martins.aprisoft.de 9.99.15 NetBSD 9.99.15 (GENERIC) #24: Fri Oct 11 18:56:14 CEST 2019 martin%martins.aprisoft.de@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:

I have a machine where the firmware (after I disabled the startup logo) comes
up in 800x600 mode and genfb picks this up (the RX480 in there is not 
supported yet).

This works so far.

When I switch graphic resolution in efiboot using "gop 0" all is fine
while in efiboot, but as soon as the kernel start printing things, the
display is totally broken (random green on black pixels untill userland
takes over, completely blan screen once xdm fires up X).

genfb0 at pci8 dev 0 function 0: vendor 1002 product 67df (rev. 0xc7)
genfb0: framebuffer at 0xe0000000, size 3840x2160, depth 32, stride 15360
genfb0: shadow framebuffer enabled, size 32400 KB
wsdisplay0 at genfb0 kbdmux 1: console (default, vt100 emulation)
wsmux1: connecting to wsdisplay0
drm at genfb0 not configured


>How-To-Repeat:
s/a

>Fix:
n/a