Re: linux-4.4 bisected: kwin5 stuck on kde5 loading screen with radeon

[Mario Kleiner]

On 01/22/2016 07:29 PM, Mario Kleiner wrote:
> On 01/22/2016 04:18 PM, Ville Syrjälä wrote:
> > On Fri, Jan 22, 2016 at 12:06:00PM +0900, Michel Dänzer wrote:
> > > [ Trimming KDE folks from Cc ]
> > >
> > > On 21.01.2016 19:09, Daniel Vetter wrote:
> > > > On Thu, Jan 21, 2016 at 05:36:46PM +0900, Michel Dänzer wrote:
> > > > > On 21.01.2016 16:58, Daniel Vetter wrote:
> > > > > > Can you please point me at the vblank on/off jump bug please?
> > > > >
> > > > > AFAIR I originally reported it in response to
> > > > > http://lists.freedesktop.org/archives/dri-devel/2015-August/087841.html
> > > > >
> > > > > , but I can't find that in the archives, so maybe that was just on
> > > > > IRC.
> > > > > See
> > > > > http://lists.freedesktop.org/archives/dri-devel/2016-January/099122.html
> > > > >
> > > > > . Basically, I ran into the bug fixed by your patch because the
> > > > > counter
> > > > > jumped forward on every DPMS off, so it hit the 32-bit boundary after
> > > > > just a few days.
> > > >
> > > > Ok, so just uncovered the overflow bug.
> > >
> > > Not sure what you mean by "just", but to be clear: The drm_vblank_on/off
> > > counter jumping bug (similar to the bug this thread is about), which
> > > exposed the overflow bug, is still alive and kicking in 4.5. It seems
> > > to happen when turning off the CRTC:
> > >
> > > [drm:drm_update_vblank_count] updating vblank count on crtc 0:
> > > current=218104694, diff=0, hw=916 hw_last=916
> > > [drm:radeon_get_vblank_counter_kms] crtc 0: dist from vblank start 3
> > > [drm:drm_calc_vbltimestamp_from_scanoutpos] crtc 0 : v 0x7
> > > p(2199,-45)@ 7304.307354 -> 7304.308006 [e 0 us, 0 rep]
> > > [drm:radeon_get_vblank_counter_kms] crtc 0: dist from vblank start 3
> > > [drm:drm_update_vblank_count] updating vblank count on crtc 0:
> > > current=218104694, diff=16776301, hw=1 hw_last=916
> >
> > Not sure what bug we're talking about here, but here the hw counter
> > clearly jumps backwards.
> >
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 3
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 3
> > > [drm:drm_update_vblank_count] updating vblank count on crtc 1:
> > > current=0, diff=0, hw=0 hw_last=0
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 3
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 3
> > > [drm:drm_update_vblank_count] updating vblank count on crtc 2:
> > > current=0, diff=0, hw=0 hw_last=0
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 3
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 3
> > > [drm:drm_update_vblank_count] updating vblank count on crtc 3:
> > > current=0, diff=0, hw=0 hw_last=0
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 1
> > > [drm:drm_calc_vbltimestamp_from_scanoutpos] crtc 0 : v 0x1 p(0,0)@
> > > 7304.317140 -> 7304.317140 [e 0 us, 0 rep]
> > > [drm:radeon_get_vblank_counter_kms] Query failed! stat 1
> > > [drm:drm_update_vblank_count] updating vblank count on crtc 0:
> > > current=234880995, diff=16777215, hw=0 hw_last=1
> >
> > Same here.
> >
> > These things just don't happen on i915 because drm_vblank_off() and
> > drm_vblank_on() are always called around the times when the hw counter
> > might get reset. Or at least that's how it should be.
>
> Fwiw, testing the HD-57570 single display with my patch that uses
> drm_vblank_off/on() in the DPMS OFF/ON path of radeon-kms does show
> hardware counter reset to zero as expected, but no jumps of software
> vblank counter. So with that vblank_off/on placement it seems to work
> nicely here.
>
> -mario

I spoke too early. The jump doesn't happen when i change video modes - 
video resolution / refresh rate etc, despite hw counter reset. But if i 
just disable and then reenable a display, the software counter jumps.

-mario