Re: [Intel-gfx] [PATCH 1/2] drm/i915/display/fbc: Make fences a nice-to-have for GEN9+

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

On Wed, Jan 29, 2020 at 01:44:49PM +0200, Ville Syrjälä wrote:
> On Tue, Jan 28, 2020 at 03:52:40PM -0800, José Roberto de Souza wrote:
> > dGFX have local memory so it do not have aperture and do not support
> > CPU fences but even for iGFX it have a small number of fences.
> > 
> > As replacement for fences to track frontbuffer modifications by CPU
> > we have a software tracking that is already in used by FBC and PSR.
> > PSR don't support fences so it shows that this tracking is reliable.
> > 
> > So lets make fences a nice-to-have to activate FBC for GEN9+(as we
> > only have a good CI coverage for GEN9+), this will allow us to enable
> > FBC for dGFXs and iGFXs even when there is no available fence.
> > 
> > intel_fbc_hw_tracking_covers_screen() maybe can also have the same
> > treatment as fences but BSpec is not clear if the size limitation is
> > for hardware tracking or general use of FBC and I don't have a 5K
> > display to test it, so keeping as is for safety.
> > 
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_fbc.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> > index 2a3f1333c8ff..1f0d24a1dec1 100644
> > --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> > +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> > @@ -717,11 +717,15 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
> >  		return false;
> >  	}
> >  
> > -	/* The use of a CPU fence is mandatory in order to detect writes
> > -	 * by the CPU to the scanout and trigger updates to the FBC.
> > +	/* The use of a CPU fence is one of two ways to detect writes by the
> > +	 * CPU to the scanout and trigger updates to the FBC.
> > +	 *
> > +	 * The other method is by software tracking(see
> > +	 * intel_fbc_invalidate/flush()), it will manually notify FBC and nuke
> > +	 * the current compressed buffer and recompress it.
> >  	 *
> >  	 * Note that is possible for a tiled surface to be unmappable (and
> > -	 * so have no fence associated with it) due to aperture constaints
> > +	 * so have no fence associated with it) due to aperture constraints
> >  	 * at the time of pinning.
> >  	 *
> >  	 * FIXME with 90/270 degree rotation we should use the fence on
> > @@ -730,7 +734,7 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
> >  	 * For now this will effecively disable FBC with 90/270 degree
> >  	 * rotation.
> >  	 */
> > -	if (cache->fence_id < 0) {
> > +	if (cache->fence_id < 0 && INTEL_GEN(dev_priv) < 9) {
> 
> Not enough. We need to check that the tiling format is actually supported.

Actually not sure if all of them are or not. IIRC some docs just said
X/Y tile is supported (and in some other place linear was also listed).

> Also the tracking stuff is busted in intel ddx so need to get
> https://patchwork.freedesktop.org/series/70636/ merged somehow.
> 
> >  		fbc->no_fbc_reason = "framebuffer not tiled or fenced";
> >  		return false;
> >  	}
> > -- 
> > 2.25.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel

-- 
Ville Syrjälä
Intel
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