port-amd64/54294: Continued kernel errors from drm/i915 problems

[arthurbarlow%gmail.com@localhost]

>Number:         54294
>Category:       port-amd64
>Synopsis:       Continued kernel errors from drm/i915 problems
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 13 14:35:00 +0000 2019
>Originator:     Arthur Barlow
>Release:        8.99.43 June-13-2019
>Organization:
NA
>Environment:
NetBSD fama.Home 8.99.43 NetBSD 8.99.43 (MYKERNEL) #0: Sun Jun  9 22:52:01 BST 2019  root%fama.Home@localhost:/usr/obj/sys/arch/amd64/compile/MYKERNEL amd64

>Description:
I get two different kernel errors from the intel_sprite.c code. The first and most common is:

[ 148206.6236226] kern error: [drm:(/usr/src/sys/external/bsd/drm2/dist/drm/i915/intel_sprite.c:132)intel_pipe_update_start] *ERROR* Potential atomic update failure on pipe A: -35

The second one is:

[ 148794.5234694] kern error: [drm:(/usr/src/sys/external/bsd/drm2/dist/drm/i915/intel_sprite.c:205)intel_pipe_update_end] *ERROR* Atomic update failure on pipe A (start=874637 end=874638) time 2 us, min 763, max 767, scanline start 765, end 768

I've noticed in the source code that there are a number of:

#ifdef ___NetBSD___

statements.  The first error, as you can see, happens at line 132, which is in one of those ifdefs.
>How-To-Repeat:
Open a browser like Firefox, Midori, or in my case Seamonkey.  Open a couple of tabs and go to a few links.  The errors show up in the xconsole.
>Fix: