Re: [PATCH 1/2] drm/i915: Force a LUT update in intel_initial_commit()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Nov 20, 2018 at 02:25:40PM -0800, Rodrigo Vivi wrote:
> On Tue, Nov 20, 2018 at 03:54:49PM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > If we force a plane update to fix up our half populated plane state
> > we'll also force on the pipe gamma for the plane (since we always
> > enable pipe gamma currently). If the BIOS hasn't programmed a sensible
> > LUT into the hardware this will cause the image to become corrupted.
> > Typical symptoms are a purple/yellow/etc. flash when the driver loads.
> > 
> > To avoid this let's program something sensible into the LUT when
> > we do the plane update. In the future I plan to add proper plane
> > gamma enable readout so this is just a temporary measure.
> 
> Since this is temporary and marked with FIXME and Hans confirmed
> it solves the best behaviour let's move with this.
> 
> But I'm wondering if there is no way to minimize this instead of
> forcing this to every commit for each crtc...

It's just for the first commit we do when loading the driver.

> 
> Anyway,
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> 
> > 
> > Cc: Hans de Goede <hdegoede@redhat.com>
> > Fixes: 516a49cc1946 ("drm/i915: Fix assert_plane() warning on bootup with external display")
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 132e978227fb..60c1e54285c1 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -15011,6 +15011,14 @@ static int intel_initial_commit(struct drm_device *dev)
> >  			ret = drm_atomic_add_affected_planes(state, crtc);
> >  			if (ret)
> >  				goto out;
> > +
> > +			/*
> > +			 * FIXME hack to force a LUT update to avoid the
> > +			 * plane update forcing the pipe gamma on without
> > +			 * having a proper LUT loaded. Remove once we
> > +			 * have readout for pipe gamma enable.
> > +			 */
> > +			crtc_state->color_mgmt_changed = true;
> >  		}
> >  	}
> >  
> > -- 
> > 2.18.1
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel
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