drm/i915: Set scaler mode for NV12

This patch sets appropriate scaler mode for NV12 format.
In this mode, skylake scaler does either chroma-upsampling or
chroma-upsampling and resolution scaling

v2: Review comments from Ville addressed
NV12 case to be checked first for setting
the scaler

v3: Rebased (me)

v4: Rebased (me)

v5: Missed the Tested-by/Reviewed-by in the previous series
Adding the same to commit message in this version.

v6: Rebased (me)

v7: Rebased (me)

v8: Rebased (me)
Restricting the NV12 change for scaler to BXT and KBL
in this series.

v9: Rebased (me)

v10: As of now, NV12 has been tested on Gen9 and Gen10. However,
code is applicable to all GEN >= 9. Hence making
that change to keep it generic.
Comments under v8 is not valid anymore.

v11: Addressed review comments by Shashank Sharma.
For Gen10+, the scaler mode to be set it planar or normal
(single bit). Changed the code to be applicable to all
Gen.

v12: Addressed review comments from Shashank Sharma
For Gen9 (apart from GLK) bits 28:29 to be programmed
in PS_CTRL for NV12. For GLK and Gen10+, bit 29 to be set
for all Planar.

v13: Addressed review comments from Juha-Pekka Heikkila
"NV12 not to be supported by SKL"
Adding Reviewed by tag from Shashank Shamr

v14: Added reviewed by from Juha-Pekka Heikkila

v15: Rebased the series
Tested-by: Clinton Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Clinton Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
Signed-off-by: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1523245273-30264-13-git-send-email-vidya.srinivas@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -6664,6 +6664,8 @@ enum {
 #define PS_SCALER_MODE_MASK (3 << 28)
 #define PS_SCALER_MODE_DYN  (0 << 28)
 #define PS_SCALER_MODE_HQ  (1 << 28)
+#define SKL_PS_SCALER_MODE_NV12 (2 << 28)
+#define PS_SCALER_MODE_PLANAR (1 << 29)
 #define PS_PLANE_SEL_MASK  (7 << 25)
 #define PS_PLANE_SEL(plane) (((plane) + 1) << 25)
 #define PS_FILTER_MASK         (3 << 23)

drivers/gpu/drm/i915/intel_atomic.c

@@ -328,8 +328,18 @@ int intel_atomic_setup_scalers(struct drm_i915_private *dev_priv,
 		}
 
 		/* set scaler mode */
-		if (IS_GEMINILAKE(dev_priv) || IS_CANNONLAKE(dev_priv)) {
-			scaler_state->scalers[*scaler_id].mode = 0;
+		if ((INTEL_GEN(dev_priv) >= 9) &&
+		    plane_state && plane_state->base.fb &&
+		    plane_state->base.fb->format->format ==
+		    DRM_FORMAT_NV12) {
+			if (INTEL_GEN(dev_priv) == 9 &&
+			    !IS_GEMINILAKE(dev_priv) &&
+			    !IS_SKYLAKE(dev_priv))
+				scaler_state->scalers[*scaler_id].mode =
+					SKL_PS_SCALER_MODE_NV12;
+			else
+				scaler_state->scalers[*scaler_id].mode =
+					PS_SCALER_MODE_PLANAR;
 		} else if (num_scalers_need == 1 && intel_crtc->pipe != PIPE_C) {
 			/*
 			 * when only 1 scaler is in use on either pipe A or B,