drm/i915/fbc: Require linear fb stride to be multiple of 512 bytes on gen9/glk

Display WA #1105 says that FBC requires PLANE_STRIDE to be a multiple
of 512 bytes on gen9 and glk.

This is definitely true for glk as certain tests (such as
igt/kms_big_fb/linear-16bpp-rotate-0) are now failing when the
display resolution results in a plane stride which is not a
multiple of 512 bytes.

Curiously I was not able to reproduce this on a KBL. First I
suspected that our use of the FBC override stride explain this,
but after trying to use the override stride on glk the test
still failed. I did try both the old CHICKEN_MISC_4 way and
the new FBC_STRIDE way, neither had any effect on the result.

Anyways, we need this at least on glk. But let's trust the spec
and apply the w/a for all gen9 as well, despite being unable to
reproduce the problem.

v2: s/FBC_CHICKEN/FBC_STRIDE/ in commit msg

Cc: José Roberto de Souza <jose.souza@intel.com>
Fixes: 691f7ba5 ("drm/i915/display/fbc: Make fences a nice-to-have for GEN9+")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200429101034.8208-2-ville.syrjala@linux.intel.comReviewed-by: Matt Roper <matthew.d.roper@intel.com>

drivers/gpu/drm/i915/display/intel_fbc.c

@@ -564,7 +564,7 @@ void intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv)
 }
 
 static bool stride_is_valid(struct drm_i915_private *dev_priv,
-			    unsigned int stride)
+			    u64 modifier, unsigned int stride)
 {
 	/* This should have been caught earlier. */
 	if (drm_WARN_ON_ONCE(&dev_priv->drm, (stride & (64 - 1)) != 0))
@@ -580,6 +580,11 @@ static bool stride_is_valid(struct drm_i915_private *dev_priv,
 	if (IS_GEN(dev_priv, 4) && !IS_G4X(dev_priv) && stride < 2048)
 		return false;
 
+	/* Display WA #1105: skl,bxt,kbl,cfl,glk */
+	if (IS_GEN(dev_priv, 9) &&
+	    modifier == DRM_FORMAT_MOD_LINEAR && stride & 511)
+		return false;
+
 	if (stride > 16384)
 		return false;
 
@@ -810,7 +815,7 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
 		return false;
 	}
 
-	if (!stride_is_valid(dev_priv, cache->fb.stride)) {
+	if (!stride_is_valid(dev_priv, cache->fb.modifier, cache->fb.stride)) {
 		fbc->no_fbc_reason = "framebuffer stride not supported";
 		return false;
 	}