drm/i915: Display WA 827

Display WA 827 applies to GEN9 (excluede GLK) and CNL.
Switching the plane format from NV12 to RGB and leaving system idle
results in display underrun and corruption.
WA: Set the bit 15 & bit 19 to 1b in the CLKGATE_DIS_PSL
register for the pipe in which NV12 plane is enabled.

v2: Addressed review comments from Maarten and
Juha-Pekka Heikkila. Added reviewed by from
Juha-Pekka Heikkila.

v3: Rebased the series

Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.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/1523245273-30264-11-git-send-email-vidya.srinivas@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -3824,6 +3824,9 @@ enum {
 #define _CLKGATE_DIS_PSL_A		0x46520
 #define _CLKGATE_DIS_PSL_B		0x46524
 #define _CLKGATE_DIS_PSL_C		0x46528
+#define   DUPS1_GATING_DIS		(1 << 15)
+#define   DUPS2_GATING_DIS		(1 << 19)
+#define   DUPS3_GATING_DIS		(1 << 23)
 #define   DPF_GATING_DIS		(1 << 10)
 #define   DPF_RAM_GATING_DIS		(1 << 9)
 #define   DPFR_GATING_DIS		(1 << 8)

drivers/gpu/drm/i915/intel_display.c

@@ -488,6 +488,21 @@ static const struct intel_limit intel_limits_bxt = {
 	.p2 = { .p2_slow = 1, .p2_fast = 20 },
 };
 
+static void
+skl_wa_clkgate(struct drm_i915_private *dev_priv, int pipe, bool enable)
+{
+	if (IS_SKYLAKE(dev_priv))
+		return;
+
+	if (enable)
+		I915_WRITE(CLKGATE_DIS_PSL(pipe),
+			   DUPS1_GATING_DIS | DUPS2_GATING_DIS);
+	else
+		I915_WRITE(CLKGATE_DIS_PSL(pipe),
+			   I915_READ(CLKGATE_DIS_PSL(pipe)) &
+			   ~(DUPS1_GATING_DIS | DUPS2_GATING_DIS));
+}
+
 static bool
 needs_modeset(const struct drm_crtc_state *state)
 {
@@ -5103,6 +5118,8 @@ static bool hsw_post_update_enable_ips(const struct intel_crtc_state *old_crtc_s
 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);
+	struct drm_device *dev = crtc->base.dev;
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_atomic_state *old_state = old_crtc_state->base.state;
 	struct intel_crtc_state *pipe_config =
 		intel_atomic_get_new_crtc_state(to_intel_atomic_state(old_state),
@@ -5125,13 +5142,22 @@ static void intel_post_plane_update(struct intel_crtc_state *old_crtc_state)
 							 to_intel_plane(primary));
 		struct intel_plane_state *old_primary_state =
 			to_intel_plane_state(old_pri_state);
+		struct drm_framebuffer *fb = primary_state->base.fb;
 
 		intel_fbc_post_update(crtc);
 
 		if (primary_state->base.visible &&
 		    (needs_modeset(&pipe_config->base) ||
 		     !old_primary_state->base.visible))
 			intel_post_enable_primary(&crtc->base, pipe_config);
+
+		/* Display WA 827 */
+		if ((INTEL_GEN(dev_priv) == 9 && !IS_GEMINILAKE(dev_priv)) ||
+		    IS_CANNONLAKE(dev_priv)) {
+			if (fb && fb->format->format == DRM_FORMAT_NV12)
+				skl_wa_clkgate(dev_priv, crtc->pipe, false);
+		}
+
 	}
 }
 
@@ -5158,6 +5184,14 @@ static void intel_pre_plane_update(struct intel_crtc_state *old_crtc_state,
 							 to_intel_plane(primary));
 		struct intel_plane_state *old_primary_state =
 			to_intel_plane_state(old_pri_state);
+		struct drm_framebuffer *fb = primary_state->base.fb;
+
+		/* Display WA 827 */
+		if ((INTEL_GEN(dev_priv) == 9 && !IS_GEMINILAKE(dev_priv)) ||
+		    IS_CANNONLAKE(dev_priv)) {
+			if (fb && fb->format->format == DRM_FORMAT_NV12)
+				skl_wa_clkgate(dev_priv, crtc->pipe, true);
+		}
 
 		intel_fbc_pre_update(crtc, pipe_config, primary_state);
 		/*