kern/60909: ThinkPad T61 with nvidia fails with nouveau in 10.2 and 11,0, works 9.5

["rm%gnu.org@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60909
>Category:       kern
>Synopsis:       ThinkPad T61 with nvidia fails with nouveau in 10.2 and 11,0, works 9.5
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Oct 20 19:15:00 +0000 2026
>Originator:     Riccardo
>Release:        11.0
>Organization:
>Environment:
NetBSD osgiliath 11.0 NetBSD 11.0 (GENERIC) #0: Thu Jul 30 15:23:12 UTC 2026  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

>Description:
NetBSD 11.0 (but problems appeared in 10.2 already, 9.x series works up to current 9.5) fails to initialize nouveau framebuffer.
Display stops in text mode when nouveau should complete framebuffer loading and switch over to framebuffer

System actually boots and does not hang, it is reachable through ssh/telnet and responds to power-off button.

vga0 at pci1 dev 0 function 0: NVIDIA Quadro NVS 140M (rev. 0xa1)

[     4.272769] nouveau0: info: NVIDIA G86 (086900a2)
[     4.292786] nouveau0: info: bios: version 60.86.3e.00.00
[     4.312800] nouveau0: info: fb: 128 MiB GDDR3
[     4.342820] nouveau0: info: DRM: VRAM: 128 MiB
[     4.342820] nouveau0: info: DRM: GART: 1048576 MiB

>How-To-Repeat:
just boot stock generic kernel on said machine and/or upgrade from existing system that worked.
>Fix:
No Fix known.
Boot of 9.5 CD still works.
Disabling nouveau yields a functional but graphic-less system.