drm/i915/icl: Fix clockgating issue when using scalers

Fixes the clock-gating issue when pipe scaling is enabled.
(Lineage #2006604312)

V2: Fix typo in headline(Chris)
    Handle the non double buffered nature of the register(Ville)
V3: Fix checkpatch warning. BAT failure for V2 on gen3 looks unrelated.
V4: Split the icl and skl wa's(Ville)
V5: Split the checks for icl and skl(Ville)
V6: Correct the flipped checks in intel_pre_plane_update(Ville)
V7: Use enum for pipe and extend the WA for plane scalers(Ville)
V8: Eliminate the redundant use of pch_pfit(Ville)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Clint Taylor <clinton.a.taylor@intel.com>
Cc: Aditya Swarup <aditya.swarup@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190417185901.14833-1-radhakrishna.sripada@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -476,6 +476,7 @@ static const struct intel_limit intel_limits_bxt = {
 	.p2 = { .p2_slow = 1, .p2_fast = 20 },
 };
 
+/* WA Display #0827: Gen9:all */
 static void
 skl_wa_827(struct drm_i915_private *dev_priv, int pipe, bool enable)
 {
@@ -489,6 +490,19 @@ skl_wa_827(struct drm_i915_private *dev_priv, int pipe, bool enable)
 			   ~(DUPS1_GATING_DIS | DUPS2_GATING_DIS));
 }
 
+/* Wa_2006604312:icl */
+static void
+icl_wa_scalerclkgating(struct drm_i915_private *dev_priv, enum pipe pipe,
+		       bool enable)
+{
+	if (enable)
+		I915_WRITE(CLKGATE_DIS_PSL(pipe),
+			   I915_READ(CLKGATE_DIS_PSL(pipe)) | DPFR_GATING_DIS);
+	else
+		I915_WRITE(CLKGATE_DIS_PSL(pipe),
+			   I915_READ(CLKGATE_DIS_PSL(pipe)) & ~DPFR_GATING_DIS);
+}
+
 static bool
 needs_modeset(const struct drm_crtc_state *state)
 {
@@ -5527,6 +5541,16 @@ static bool needs_nv12_wa(struct drm_i915_private *dev_priv,
 	return false;
 }
 
+static bool needs_scalerclk_wa(struct drm_i915_private *dev_priv,
+			       const struct intel_crtc_state *crtc_state)
+{
+	/* Wa_2006604312:icl */
+	if (crtc_state->scaler_state.scaler_users > 0 && IS_ICELAKE(dev_priv))
+		return true;
+
+	return false;
+}
+
 static void intel_post_plane_update(struct intel_crtc_state *old_crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(old_crtc_state->base.crtc);
@@ -5560,11 +5584,13 @@ static void intel_post_plane_update(struct intel_crtc_state *old_crtc_state)
 			intel_post_enable_primary(&crtc->base, pipe_config);
 	}
 
-	/* Display WA 827 */
 	if (needs_nv12_wa(dev_priv, old_crtc_state) &&
-	    !needs_nv12_wa(dev_priv, pipe_config)) {
+	    !needs_nv12_wa(dev_priv, pipe_config))
 		skl_wa_827(dev_priv, crtc->pipe, false);
-	}
+
+	if (needs_scalerclk_wa(dev_priv, old_crtc_state) &&
+	    !needs_scalerclk_wa(dev_priv, pipe_config))
+		icl_wa_scalerclkgating(dev_priv, crtc->pipe, false);
 }
 
 static void intel_pre_plane_update(struct intel_crtc_state *old_crtc_state,
@@ -5601,9 +5627,13 @@ static void intel_pre_plane_update(struct intel_crtc_state *old_crtc_state,
 
 	/* Display WA 827 */
 	if (!needs_nv12_wa(dev_priv, old_crtc_state) &&
-	    needs_nv12_wa(dev_priv, pipe_config)) {
+	    needs_nv12_wa(dev_priv, pipe_config))
 		skl_wa_827(dev_priv, crtc->pipe, true);
-	}
+
+	/* Wa_2006604312:icl */
+	if (!needs_scalerclk_wa(dev_priv, old_crtc_state) &&
+	    needs_scalerclk_wa(dev_priv, pipe_config))
+		icl_wa_scalerclkgating(dev_priv, crtc->pipe, true);
 
 	/*
 	 * Vblank time updates from the shadow to live plane control register