drm/i915: skylake panel fitting using shared scalers

Enabling skylake panel fitting feature using shared scalers

v2:
-added force detach parameter for pfit disable purpose (me)
-read crtc scaler state from hw state (Daniel)
-replaced both skylake_pfit_enable and disable with skylake_pfit_update (me)
-added scaler id check to intel_pipe_config_compare (Daniel)

v3:
-updated function header to kerneldoc format (Matt)
-dropped need_scaling checks (Matt)

v4:
-move clearing of scaler id from commit path to check path (Matt)
-updated colorkey checks based on recent updates (me)
-squashed scaler check while enabling colorkey to here (me)
-use values in plane_state->src as regular integers (me)
-changes made not to modify state in commit path (Matt)

v5:
-squashed helper function to update scaler users to here (Matt)
-squashed helper function to detach scaler to here (Matt, me)
-changes to align with updated scaler structures (Matt, me)

Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 589cd92..3ea68e1 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1351,6 +1351,14 @@
 	if (is_edp(intel_dp) && intel_connector->panel.fixed_mode) {
 		intel_fixed_panel_mode(intel_connector->panel.fixed_mode,
 				       adjusted_mode);
+
+		if (INTEL_INFO(dev)->gen >= 9) {
+			int ret;
+			ret = skl_update_scaler_users(intel_crtc, pipe_config, NULL, NULL, 0);
+			if (ret)
+				return ret;
+		}
+
 		if (!HAS_PCH_SPLIT(dev))
 			intel_gmch_panel_fitting(intel_crtc, pipe_config,
 						 intel_connector->panel.fitting_mode);