[Intel-gfx] Possible i915 regression with 4.4-rc

[Chris Wilson]

On Fri, Dec 04, 2015 at 12:00:08PM +0000, Dave Gordon wrote:
> On 03/12/15 21:35, Chris Wilson wrote:
> >On Thu, Dec 03, 2015 at 11:25:48PM +0200, Ville Syrjälä wrote:
> >>On Thu, Dec 03, 2015 at 10:08:05PM +0100, Takashi Iwai wrote:
> >>>On Thu, 03 Dec 2015 21:33:29 +0100,
> >>>Ville Syrjälä wrote:
> >>>>
> >>>>On Thu, Dec 03, 2015 at 09:00:55PM +0100, Takashi Iwai wrote:
> >>>>>Hi,
> >>>>>
> >>>>>I've experienced a few graphics issues recently, and I tend to believe
> >>>>>that it has happened since 4.4-rc.  Namely, after some long time usage
> >>>>>on my HSW laptop (two or three days), the mouse cursor vanished
> >>>>>suddenly.  It kept pointing but just became invisible.  Also, after
> >>>>>some S3 cycles, some glyphs on a console or on Firefox became
> >>>>>invisible, too.  The windows and graphics were shown well, and X core
> >>>>>fonts were still shown properly, too.  Switching to VT1 and back
> >>>>>didn't change the situation.
> >>>>
> >>>>I think I have a fix for this *very* annoying problem. I'v been cursing
> >>>>on irc for weeks about it, until I finally got off my arse and debugged
> >>>>it.
> >>>>
> >>>>I pushed out my my cursor branch:
> >>>>git://github.com/vsyrjala/linux.git disappearing_cursor_fix
> >>>>
> >>>>It has lots of other junk too, but it should be just there two that fix it:
> >>>>59f65fa270fb ("drm/i915: Kill intel_crtc->cursor_bo")
> >>>>25651a198d17 ("drm/i915: Drop the broken curcor base==0 special casing")
> >>>>
> >>>>Unfortunatleey I've managed to keep myself busy on other stuff, so didn't
> >>>>send them out yet. Maybe tomorrow...
> >>>
> >>>Great, I'll try them out now.  But these look like fixing only the
> >>>cursor issue.  Would they cover also the missing glyphs I experienced?
> >>
> >>No. That's either userland, or some object/context/etc. getting corrupted
> >>I think. I've had something like that occasionally too after some number of
> >>suspend cycles, and usually fbcon is dead at that point too (just get a
> >>black screen on VT switch).
> >>
> >>I think we had some bug with not properly pinning the fbdev buffer which
> >>could explain things getting corrupted. Chris had a fix I think, but I'm
> >>not sure if that went anywhere. Chris?
> >
> >Jani keeps refusing it :). But it's not the issue with the missing
> >glyphs. The missing glyphs is the kernel dropping rendering, or that
> >rendering not being flushed out to memory across the suspend as it is just
> >texture corruption. The glyph cache only slowly changes, so corruption
> >tends to be visible for some time.  An alternative explanation would be
> >that GPU state is not restored upon resume that only (visibly) effects
> >glyph rendering (and portions thereof). Lost rendering is a simpler
> >explanation.
> >-Chris
> 
> Could also be down to certain objects getting their contents
> discarded when evicted (due to not being marked dirty), for which I
> posted a fix "Always mark GEM objects as dirty when written by the
> CPU" a few days ago?

Grasping at straws?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre