drm/i915: Extract intel_dbuf_mdclk_cdclk_ratio_update()

As of Xe2LPD, it is now possible to select the source of the MDCLK
as either the CD2XCLK or the CDCLK PLL.

Previous display IPs were hardcoded to use the CD2XCLK. For those, the
ratio between MDCLK and CDCLK remained constant, namely 2. For Xe2LPD,
when we select the CDCLK PLL as the source, the ratio will vary
according to the squashing configuration (since the cd2x divisor is
fixed for all supported configurations).

To help the transition to supporting changes in the ratio, extract the
function intel_dbuf_mdclk_cdclk_ratio_update() from the existing logic
and call it using 2 as hardcoded ratio. Upcoming changes will use that
function for updates in the ratio due to CDCLK changes.

Bspec: 50057, 69445, 49213, 68868
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240312163639.172321-5-gustavo.sousa@intel.comSigned-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

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

@@ -3530,6 +3530,21 @@ int intel_dbuf_init(struct drm_i915_private *i915)
 	return 0;
 }
 
+static void intel_dbuf_mdclk_cdclk_ratio_update(struct drm_i915_private *i915,
+						u8 ratio,
+						bool joined_mbus)
+{
+	enum dbuf_slice slice;
+
+	if (joined_mbus)
+		ratio *= 2;
+
+	for_each_dbuf_slice(i915, slice)
+		intel_de_rmw(i915, DBUF_CTL_S(slice),
+			     DBUF_MIN_TRACKER_STATE_SERVICE_MASK,
+			     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.
@@ -3537,8 +3552,7 @@ int intel_dbuf_init(struct drm_i915_private *i915)
 static void update_mbus_pre_enable(struct intel_atomic_state *state)
 {
 	struct drm_i915_private *i915 = to_i915(state->base.dev);
-	u32 mbus_ctl, dbuf_min_tracker_val;
-	enum dbuf_slice slice;
+	u32 mbus_ctl;
 	const struct intel_dbuf_state *dbuf_state =
 		intel_atomic_get_new_dbuf_state(state);
 
@@ -3549,24 +3563,18 @@ static void update_mbus_pre_enable(struct intel_atomic_state *state)
 	 * TODO: Implement vblank synchronized MBUS joining changes.
 	 * Must be properly coordinated with dbuf reprogramming.
 	 */
-	if (dbuf_state->joined_mbus) {
+	if (dbuf_state->joined_mbus)
 		mbus_ctl = MBUS_HASHING_MODE_1x4 | MBUS_JOIN |
 			MBUS_JOIN_PIPE_SELECT_NONE;
-		dbuf_min_tracker_val = DBUF_MIN_TRACKER_STATE_SERVICE(3);
-	} else {
+	else
 		mbus_ctl = MBUS_HASHING_MODE_2x2 |
 			MBUS_JOIN_PIPE_SELECT_NONE;
-		dbuf_min_tracker_val = DBUF_MIN_TRACKER_STATE_SERVICE(1);
-	}
 
 	intel_de_rmw(i915, MBUS_CTL,
 		     MBUS_HASHING_MODE_MASK | MBUS_JOIN |
 		     MBUS_JOIN_PIPE_SELECT_MASK, mbus_ctl);
 
-	for_each_dbuf_slice(i915, slice)
-		intel_de_rmw(i915, DBUF_CTL_S(slice),
-			     DBUF_MIN_TRACKER_STATE_SERVICE_MASK,
-			     dbuf_min_tracker_val);
+	intel_dbuf_mdclk_cdclk_ratio_update(i915, 2, dbuf_state->joined_mbus);
 }
 
 void intel_dbuf_pre_plane_update(struct intel_atomic_state *state)