[Intel-gfx] [PATCH] drm/i915: Fix scaling check for 90/270 degree plane rotation

[Daniel Vetter]

On Thu, Oct 27, 2016 at 08:46:50AM +0100, Tvrtko Ursulin wrote:
> 
> On 25/10/2016 13:45, ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Starting from commit b63a16f6cd89 ("drm/i915: Compute display surface
> > offset in the plane check hook for SKL+") we've already rotated the src
> > coordinates by 270 degrees by the time we check if a scaler is needed
> > or not, so we must not account for the rotation a second time.
> > Previously we did these steps in the opposite order and hence the
> > scaler check had to deal with rotation itself. The double rotation
> > handling causes us to enable a scaler pretty much every time 90/270
> > degree plane rotation is requested, leading to fuzzier fonts and whatnot.
> > 
> > Cc: Sivakumar Thulasimani <sivakumar.thulasimani at intel.com>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Cc: drm-intel-fixes at lists.freedesktop.org
> > Reported-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Fixes: b63a16f6cd89 ("drm/i915: Compute display surface offset in the plane check hook for SKL+")
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 14 ++++++++------
> >  1 file changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 5a036999487b..587cd604ce92 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -4671,7 +4671,7 @@ static void cpt_verify_modeset(struct drm_device *dev, int pipe)
> > 
> >  static int
> >  skl_update_scaler(struct intel_crtc_state *crtc_state, bool force_detach,
> > -		  unsigned scaler_user, int *scaler_id, unsigned int rotation,
> > +		  unsigned scaler_user, int *scaler_id,
> >  		  int src_w, int src_h, int dst_w, int dst_h)
> >  {
> >  	struct intel_crtc_scaler_state *scaler_state =
> > @@ -4680,9 +4680,12 @@ skl_update_scaler(struct intel_crtc_state *crtc_state, bool force_detach,
> >  		to_intel_crtc(crtc_state->base.crtc);
> >  	int need_scaling;
> > 
> > -	need_scaling = drm_rotation_90_or_270(rotation) ?
> > -		(src_h != dst_w || src_w != dst_h):
> > -		(src_w != dst_w || src_h != dst_h);
> > +	/*
> > +	 * Src coordinates are already rotated by 270 degrees for
> > +	 * the 90/270 degree plane rotation cases (to match the
> > +	 * GTT mapping), hence no need to account for rotation here.
> > +	 */
> > +	need_scaling = src_w != dst_w || src_h != dst_h;
> > 
> >  	/*
> >  	 * if plane is being disabled or scaler is no more required or force detach
> > @@ -4749,7 +4752,7 @@ int skl_update_scaler_crtc(struct intel_crtc_state *state)
> >  		      intel_crtc->pipe, SKL_CRTC_INDEX);
> > 
> >  	return skl_update_scaler(state, !state->base.active, SKL_CRTC_INDEX,
> > -		&state->scaler_state.scaler_id, DRM_ROTATE_0,
> > +		&state->scaler_state.scaler_id,
> >  		state->pipe_src_w, state->pipe_src_h,
> >  		adjusted_mode->crtc_hdisplay, adjusted_mode->crtc_vdisplay);
> >  }
> > @@ -4783,7 +4786,6 @@ static int skl_update_scaler_plane(struct intel_crtc_state *crtc_state,
> >  	ret = skl_update_scaler(crtc_state, force_detach,
> >  				drm_plane_index(&intel_plane->base),
> >  				&plane_state->scaler_id,
> > -				plane_state->base.rotation,
> >  				drm_rect_width(&plane_state->base.src) >> 16,
> >  				drm_rect_height(&plane_state->base.src) >> 16,
> >  				drm_rect_width(&plane_state->base.dst),
> > 
> 
> Tested-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> After this only the DRM core revert remains. Is that one something of a
> workaround or actually could get in?

We could add an fb_changed boolean to drm_plane_state which drives can use
to override the drm helper's decision whether to call prepare_plane. And
then i915 could set that if rotation changes.

That's probably the fastest quick fix (but won't type that since I'll be
travelling next week).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch