[igt-dev] [PATCH i-g-t] igt/kms_frontbuffer_tracking: Skip tests if FBC was disabled

[Lofstedt, Marta]

> -----Original Message-----
> From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> Sent: Tuesday, March 6, 2018 1:03 PM
> To: Nikula, Jani <jani.nikula at intel.com>; Lofstedt, Marta
> <marta.lofstedt at intel.com>; igt-dev at lists.freedesktop.org
> Cc: Zanoni, Paulo R <paulo.r.zanoni at intel.com>; Lankhorst, Maarten
> <maarten.lankhorst at intel.com>
> Subject: RE: [igt-dev] [PATCH i-g-t] igt/kms_frontbuffer_tracking: Skip tests if
> FBC was disabled
> 
> Quoting Jani Nikula (2018-03-06 10:55:02)
> > On Tue, 06 Mar 2018, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > > Quoting Lofstedt, Marta (2018-03-06 10:39:04)
> > >>
> > >>
> > >> > -----Original Message-----
> > >> > From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> > >> > Sent: Tuesday, March 6, 2018 11:32 AM
> > >> > To: Lofstedt, Marta <marta.lofstedt at intel.com>; igt-
> > >> > dev at lists.freedesktop.org
> > >> > Subject: Re: [igt-dev] [PATCH i-g-t]
> > >> > igt/kms_frontbuffer_tracking: Skip tests if FBC was disabled
> > >> >
> > >> > Quoting Marta Lofstedt (2018-03-06 09:24:57)
> > >> > > If FBC has been disabled in the system due to previous
> > >> > > malfuction, we would save time on CI if we bail out early.
> > >> > >
> > >> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105359
> > >> > > Signed-off-by: Marta Lofstedt <marta.lofstedt at intel.com>
> > >> >
> > >> > Hmm, FBC starts inactive on a system, so we would need to ensure
> > >> > that we enabled FBC and did a proper modeset first and wait for
> > >> > FBC to be enabled first.
> > >>
> > >> On the SKL NUCi5 system I have been running this on, the FBC disabled
> sysfs, isn't re-set after a modeset. Maybe this is a driver error that should not
> be hidden by me suggesting to skip the tests.
> > >
> > > It may just be that we see the same error. Some errors like
> > > underruns permanently disable FBC (afaik).

Is, one underrun and forever no FBC is how we want it in the driver?

> >
> > Could we add a way to manually force enable FBC in that case? debugfs?
> 
> Or a (CRTC?) property, userspace sets it to desired, kernel updates to
> off/on?
> (Now that is a very old dream.)
> -Chris