drm/i915: Make sure plane dims are correct for UV CCS planes

As intel_fb_plane_get_subsampling() returns the subsampling factor wrt.
its main plane, for a CCS plane we need to apply both the main and the
CCS plane's subsampling factor on the FB's dimensions to get the CCS
plane's dimensions.

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191231233756.18753-5-imre.deak@intel.com

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

@@ -2913,11 +2913,15 @@ intel_fb_check_ccs_xy(struct drm_framebuffer *fb, int ccs_plane, int x, int y)
 static void
 intel_fb_plane_dims(int *w, int *h, struct drm_framebuffer *fb, int color_plane)
 {
+	int main_plane = is_ccs_plane(fb, color_plane) ?
+			 ccs_to_main_plane(fb, color_plane) : 0;
+	int main_hsub, main_vsub;
 	int hsub, vsub;
 
+	intel_fb_plane_get_subsampling(&main_hsub, &main_vsub, fb, main_plane);
 	intel_fb_plane_get_subsampling(&hsub, &vsub, fb, color_plane);
-	*w = fb->width / hsub;
-	*h = fb->height / vsub;
+	*w = fb->width / main_hsub / hsub;
+	*h = fb->height / main_vsub / vsub;
 }
 
 /*