drm/i915/display/adlp: Adjust MBUS DBOX BW and B credits

Alderlake-P has different MBUS DBOX BW and B credits than other
platforms, so here setting it properly.

BSpec: 49213
BSpec: 50343
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Caz Yokoyama <caz.yokoyama@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220330155724.255226-2-jose.souza@intel.com

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

@@ -1845,7 +1845,10 @@ static void icl_pipe_mbus_enable(struct intel_crtc *crtc, bool joined_mbus)
 	else
 		val |= MBUS_DBOX_A_CREDIT(2);
 
-	if (DISPLAY_VER(dev_priv) >= 12) {
+	if (IS_ALDERLAKE_P(dev_priv)) {
+		val |= MBUS_DBOX_BW_CREDIT(2);
+		val |= MBUS_DBOX_B_CREDIT(8);
+	} else if (DISPLAY_VER(dev_priv) >= 12) {
 		val |= MBUS_DBOX_BW_CREDIT(2);
 		val |= MBUS_DBOX_B_CREDIT(12);
 	} else {