[PATCH 4/4] drm/i915: Don't allocate extra ddb during async flip for DG2

[Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>]

In terms of async flip optimization we don't to allocate
extra ddb space, so lets skip it.

v2: - Extracted min ddb async flip check to separate function
      (Ville Syrjälä)
    - Used this function to prevent false positive WARN
      to be triggered(Ville Syrjälä)

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_pm.c | 34 ++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 5d350ddc447f..4922c9108f08 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5118,6 +5118,12 @@ static bool icl_need_wm1_wa(struct drm_i915_private *i915,
 	       (IS_DISPLAY_VER(i915, 12, 13) && plane_id == PLANE_CURSOR);
 }
 
+static bool dg2_need_min_ddb(struct drm_i915_private *i915,
+			     struct intel_crtc_state *crtc_state)
+{
+	return IS_DG2(i915) && crtc_state->uapi.async_flip;
+}
+
 static int
 skl_allocate_plane_ddb(struct intel_atomic_state *state,
 		       struct intel_crtc *crtc)
@@ -5226,9 +5232,15 @@ skl_allocate_plane_ddb(struct intel_atomic_state *state,
 			break;
 
 		rate = crtc_state->plane_data_rate[plane_id];
-		extra = min_t(u16, alloc_size,
-			      DIV64_U64_ROUND_UP(alloc_size * rate,
-						 total_data_rate));
+
+		if (dg2_need_min_ddb(dev_priv, crtc_state)) {
+			extra = 0;
+		} else {
+			extra = min_t(u16, alloc_size,
+				      DIV64_U64_ROUND_UP(alloc_size * rate,
+							 total_data_rate));
+		}
+
 		total[plane_id] = wm->wm[level].min_ddb_alloc + extra;
 		alloc_size -= extra;
 		total_data_rate -= rate;
@@ -5237,14 +5249,22 @@ skl_allocate_plane_ddb(struct intel_atomic_state *state,
 			break;
 
 		rate = crtc_state->uv_plane_data_rate[plane_id];
-		extra = min_t(u16, alloc_size,
-			      DIV64_U64_ROUND_UP(alloc_size * rate,
-						 total_data_rate));
+
+		if (dg2_need_min_ddb(dev_priv, crtc_state)) {
+			extra = 0;
+		} else {
+			extra = min_t(u16, alloc_size,
+				      DIV64_U64_ROUND_UP(alloc_size * rate,
+							 total_data_rate));
+		}
+
 		uv_total[plane_id] = wm->uv_wm[level].min_ddb_alloc + extra;
 		alloc_size -= extra;
 		total_data_rate -= rate;
 	}
-	drm_WARN_ON(&dev_priv->drm, alloc_size != 0 || total_data_rate != 0);
+
+	if (!dg2_need_min_ddb(dev_priv, crtc_state))
+		drm_WARN_ON(&dev_priv->drm, alloc_size != 0 || total_data_rate != 0);
 
 	/* Set the actual DDB start/end points for each plane */
 	start = alloc->start;
-- 
2.24.1.485.gad05a3d8e5