realtek: Add HW support for RTL931X for PIE, L2 and STP aging

We add HW support routines for the RTL931X SoC family for handling
the Packet Inspection Engine, L2 table handling and STP aging.

Signed-off-by: Sebastian Gottschall <s.gottschall@dd-wrt.com>
Signed-off-by: Birger Koblitz <git@birger-koblitz.de>

target/linux/realtek/files-5.10/drivers/net/dsa/rtl83xx/dsa.c

@@ -1304,10 +1304,28 @@ void rtl83xx_fast_age(struct dsa_switch *ds, int port)
 	mutex_unlock(&priv->reg_mutex);
 }
 
+void rtl931x_fast_age(struct dsa_switch *ds, int port)
+{
+	struct rtl838x_switch_priv *priv = ds->priv;
+
+	pr_info("%s port %d\n", __func__, port);
+	mutex_lock(&priv->reg_mutex);
+	sw_w32(port << 11, RTL931X_L2_TBL_FLUSH_CTRL + 4);
+
+	sw_w32(BIT(24) | BIT(28), RTL931X_L2_TBL_FLUSH_CTRL);
+
+	do { } while (sw_r32(RTL931X_L2_TBL_FLUSH_CTRL) & BIT (28));
+
+	mutex_unlock(&priv->reg_mutex);
+}
+
 void rtl930x_fast_age(struct dsa_switch *ds, int port)
 {
 	struct rtl838x_switch_priv *priv = ds->priv;
 
+	if (priv->family_id == RTL9310_FAMILY_ID)
+		return rtl931x_fast_age(ds, port);
+
 	pr_debug("FAST AGE port %d\n", port);
 	mutex_lock(&priv->reg_mutex);
 	sw_w32(port << 11, RTL930X_L2_TBL_FLUSH_CTRL + 4);