port-amd64/59995: i915drmkms0 and various stripes in screen xorg environment

["taittoni%gmail.com@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         59995
>Category:       port-amd64
>Synopsis:       i915drmkms0 and various stripes in screen xorg environment
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 11 21:05:00 +0000 2026
>Originator:     Toni Virtanen
>Release:        10.1 ( https://cdn.NetBSD.org/pub/pkgsrc/packages/NetBSD/amd64/10.1/All )
>Organization:
>Environment:
$ uname -a
NetBSD NetBSD.home 10.1 NetBSD 10.1 (GENERIC) #0: Mon Dec 16 13:08:11 UTC 2024  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
One kernel crash at boot. Otherwise eg. when writing in thunderbird letters form slowly. In Firefox thumbnails in tabs, images appear striped.

$ dmesg |grep drm  
[     1,032557] i915drmkms0 at pci0 dev 2 function 0: Intel Ivy Bridge Integrated Graphics Device (rev. 0x09)
[     5,096347] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[     5,126347] [drm] Driver supports precise vblank timestamp query.
[     5,146347] i915drmkms0: interrupting at msi4 vec 0 (i915drmkms0)
[     5,196347] [drm] Initialized i915 1.6.0 20200114 for i915drmkms0 on minor 0
[     5,326347] intelfb0 at i915drmkms0
[     5,326347] [drm] DRM_I915_DEBUG enabled
[     5,326347] [drm] DRM_I915_DEBUG_GEM enabled
[     5,456347] {drm:netbsd:intel_set_cpu_fifo_underrun_reporting+0x29c} *ERROR* uncleared fifo underrun on pipe A
[     5,456347] {drm:netbsd:intel_cpu_fifo_underrun_irq_handler+0x64} *ERROR* CPU pipe A FIFO underrun
[     5,456347] {drm:netbsd:intel_set_cpu_fifo_underrun_reporting+0x29c} *ERROR* uncleared fifo underrun on pipe B
[     5,456347] {drm:netbsd:intel_cpu_fifo_underrun_irq_handler+0x64} *ERROR* CPU pipe B FIFO underrun
[     5,466488] {drm:netbsd:intel_set_pch_fifo_underrun_reporting+0x14e} *ERROR* uncleared pch fifo underrun on pch transcoder A
[     5,466488] {drm:netbsd:cpt_irq_handler+0x217} *ERROR* PCH transcoder A FIFO underrun
[     5,466488] {drm:netbsd:intel_set_pch_fifo_underrun_reporting+0x14e} *ERROR* uncleared pch fifo underrun on pch transcoder B
[     5,466488] {drm:netbsd:cpt_irq_handler+0x217} *ERROR* PCH transcoder B FIFO underrun
[  1646,099668] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe B: -35
[  1646,149668] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe B: -35
[  1646,199674] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe B: -35
[  1646,249666] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe B: -35
[  2731,315248] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe A: -35
[  4631,187511] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe A: -35
[  5811,762704] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe A: -35
[  6856,558449] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe B: -35
[  7099,777459] {drm:netbsd:intel_pipe_update_start+0x2ff} *ERROR* Potential atomic update failure on pipe A: -35

>How-To-Repeat:
Happens every time.
>Fix: