drm/i915: Don't allocate extra ddb during async flip for DG2

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)

v3: - Renamed dg2_need_min_ddb to need_min_ddb thus making
      it more universal.
    - Also used DISPLAY_VER instead of IS_DG2(Ville Syrjälä)
    - Use rate = 0 instead of just setting extra = 0, thus
      letting other planes to use extra ddb and avoiding WARN
      (Ville Syrjälä)

v4: - Renamed needs_min_ddb as s/needs/use/ to match
      the wm0 counterpart(Ville Syrjälä)
    - Added plane->async_flip check to use_min_ddb(now
      passing plane as a parameter to do that)(Ville Syrjälä)
    - Account for use_min_ddb also when calculating total data rate
      (Ville Syrjälä)

v5:
    - Use for_each_intel_plane_on_crtc instead of for_each_intel_plane_id
      to get plane->async_flip check and account for all planes(Ville Syrjälä)
    - Fix line wrapping(Ville Syrjälä)
    - Set plane data rate conditionally, avoiding on redundant assignment
      (Ville Syrjälä)
    - Removed redundant whitespace(Ville Syrjälä)
    - Handle use_min_ddb case in skl_plane_relative_data_rate instead of
      icl_get_total_relative_data_rate(Ville Syrjälä)

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220124090653.14547-2-stanislav.lisovskiy@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -4906,6 +4906,17 @@ static u8 skl_compute_dbuf_slices(struct intel_crtc *crtc, u8 active_pipes)
 	return active_pipes & BIT(pipe) ? BIT(DBUF_S1) : 0;
 }
 
+static bool
+use_min_ddb(const struct intel_crtc_state *crtc_state,
+	    struct intel_plane *plane)
+{
+	struct drm_i915_private *i915 = to_i915(plane->base.dev);
+
+	return DISPLAY_VER(i915) >= 13 &&
+	       crtc_state->uapi.async_flip &&
+	       plane->async_flip;
+}
+
 static bool
 use_minimal_wm0_only(const struct intel_crtc_state *crtc_state,
 		     struct intel_plane *plane)
@@ -4935,6 +4946,14 @@ skl_plane_relative_data_rate(const struct intel_crtc_state *crtc_state,
 	if (plane->id == PLANE_CURSOR)
 		return 0;
 
+	/*
+	 * We calculate extra ddb based on ratio plane rate/total data rate
+	 * in case, in some cases we should not allocate extra ddb for the plane,
+	 * so do not count its data rate, if this is the case.
+	 */
+	if (use_min_ddb(crtc_state, plane))
+		return 0;
+
 	if (color_plane == 1 &&
 	    !intel_format_info_is_yuv_semiplanar(fb->format, fb->modifier))
 		return 0;