drm/i915: Extract intel_dbuf_mbus_join_update()

Extact the stuff that writes the joining bits in MBUS_CTL
into its own function. Will help with correctly sequencing
the operations done during mbus programming.
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240402155016.13733-8-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/display/skl_watermark.c

@@ -3653,21 +3653,12 @@ void intel_dbuf_mdclk_cdclk_ratio_update(struct drm_i915_private *i915, u8 ratio
 			     DBUF_MIN_TRACKER_STATE_SERVICE(ratio - 1));
 }
 
-/*
- * Configure MBUS_CTL and all DBUF_CTL_S of each slice to join_mbus state before
- * update the request state of all DBUS slices.
- */
-static void update_mbus_pre_enable(struct intel_atomic_state *state)
+static void intel_dbuf_mbus_join_update(struct intel_atomic_state *state)
 {
 	struct drm_i915_private *i915 = to_i915(state->base.dev);
-	u32 mbus_ctl;
-	const struct intel_dbuf_state *old_dbuf_state =
-		intel_atomic_get_old_dbuf_state(state);
 	const struct intel_dbuf_state *new_dbuf_state =
 		intel_atomic_get_new_dbuf_state(state);
-
-	if (!HAS_MBUS_JOINING(i915))
-		return;
+	u32 mbus_ctl;
 
 	/*
 	 * TODO: Implement vblank synchronized MBUS joining changes.
@@ -3683,6 +3674,28 @@ static void update_mbus_pre_enable(struct intel_atomic_state *state)
 	intel_de_rmw(i915, MBUS_CTL,
 		     MBUS_HASHING_MODE_MASK | MBUS_JOIN |
 		     MBUS_JOIN_PIPE_SELECT_MASK, mbus_ctl);
+}
+
+/*
+ * Configure MBUS_CTL and all DBUF_CTL_S of each slice to join_mbus state before
+ * update the request state of all DBUS slices.
+ */
+static void update_mbus_pre_enable(struct intel_atomic_state *state)
+{
+	struct drm_i915_private *i915 = to_i915(state->base.dev);
+	const struct intel_dbuf_state *old_dbuf_state =
+		intel_atomic_get_old_dbuf_state(state);
+	const struct intel_dbuf_state *new_dbuf_state =
+		intel_atomic_get_new_dbuf_state(state);
+
+	if (!HAS_MBUS_JOINING(i915))
+		return;
+
+	/*
+	 * TODO: Implement vblank synchronized MBUS joining changes.
+	 * Must be properly coordinated with dbuf reprogramming.
+	 */
+	intel_dbuf_mbus_join_update(state);
 
 	if (DISPLAY_VER(i915) >= 20 &&
 	    old_dbuf_state->mdclk_cdclk_ratio != new_dbuf_state->mdclk_cdclk_ratio) {