drm/i915/skl: Check the DDB state at modeset

v2: Don't check DDB on pre-SKL platforms
    Don't check DDB state on disabled pipes

v3: Squash "Expose skl_ddb_get_hw_state()"

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index fbe18ae..ee744a2 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1400,6 +1400,15 @@
 	return entry->end - entry->start + 1;
 }
 
+static inline bool skl_ddb_entry_equal(const struct skl_ddb_entry *e1,
+				       const struct skl_ddb_entry *e2)
+{
+	if (e1->start == e2->start && e1->end == e2->end)
+		return true;
+
+	return false;
+}
+
 struct skl_ddb_allocation {
 	struct skl_ddb_entry plane[I915_MAX_PIPES][I915_MAX_PLANES];
 	struct skl_ddb_entry cursor[I915_MAX_PIPES];