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

[Chris Wilson]

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?

It itself is a workaround. There are more reasons why it is broken for
us than just getting rotation wrong (it breaks the render-vs-modeset
ordering, which is both ABI and required for us to prevent GPU hangs).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre