net: dsa: mv88e6xxx: write VID outside of VTU Get Next code

There is no need to write the VLAN ID before every Get Next operation,
since the VTU VID register is not cleared between calls.

Move the VID write call in a _mv88e6xxx_vtu_vid_write function outside
of _mv88e6xxx_vtu_getnext so future code could call VTU Get Next
multiple times and save a few register accesses.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx.c

@@ -1259,7 +1259,13 @@ static int _mv88e6xxx_vtu_stu_data_write(struct dsa_switch *ds,
 	return 0;
 }
 
-static int _mv88e6xxx_vtu_getnext(struct dsa_switch *ds, u16 vid,
+static int _mv88e6xxx_vtu_vid_write(struct dsa_switch *ds, u16 vid)
+{
+	return _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_VTU_VID,
+				    vid & GLOBAL_VTU_VID_MASK);
+}
+
+static int _mv88e6xxx_vtu_getnext(struct dsa_switch *ds,
 				  struct mv88e6xxx_vtu_stu_entry *entry)
 {
 	struct mv88e6xxx_vtu_stu_entry next = { 0 };
@@ -1269,11 +1275,6 @@ static int _mv88e6xxx_vtu_getnext(struct dsa_switch *ds, u16 vid,
 	if (ret < 0)
 		return ret;
 
-	ret = _mv88e6xxx_reg_write(ds, REG_GLOBAL, GLOBAL_VTU_VID,
-				   vid & GLOBAL_VTU_VID_MASK);
-	if (ret < 0)
-		return ret;
-
 	ret = _mv88e6xxx_vtu_cmd(ds, GLOBAL_VTU_OP_VTU_GET_NEXT);
 	if (ret < 0)
 		return ret;
@@ -1485,7 +1486,12 @@ int mv88e6xxx_port_vlan_add(struct dsa_switch *ds, int port, u16 vid,
 	int err;
 
 	mutex_lock(&ps->smi_mutex);
-	err = _mv88e6xxx_vtu_getnext(ds, vid - 1, &vlan);
+
+	err = _mv88e6xxx_vtu_vid_write(ds, vid - 1);
+	if (err)
+		goto unlock;
+
+	err = _mv88e6xxx_vtu_getnext(ds, &vlan);
 	if (err)
 		goto unlock;
 
@@ -1514,7 +1520,11 @@ int mv88e6xxx_port_vlan_del(struct dsa_switch *ds, int port, u16 vid)
 
 	mutex_lock(&ps->smi_mutex);
 
-	err = _mv88e6xxx_vtu_getnext(ds, vid - 1, &vlan);
+	err = _mv88e6xxx_vtu_vid_write(ds, vid - 1);
+	if (err)
+		goto unlock;
+
+	err = _mv88e6xxx_vtu_getnext(ds, &vlan);
 	if (err)
 		goto unlock;
 
@@ -1558,7 +1568,11 @@ static int _mv88e6xxx_port_vtu_getnext(struct dsa_switch *ds, int port, u16 vid,
 		if (vid == 4095)
 			return -ENOENT;
 
-		err = _mv88e6xxx_vtu_getnext(ds, vid, entry);
+		err = _mv88e6xxx_vtu_vid_write(ds, vid);
+		if (err)
+			return err;
+
+		err = _mv88e6xxx_vtu_getnext(ds, entry);
 		if (err)
 			return err;
 
@@ -1584,7 +1598,12 @@ int mv88e6xxx_vlan_getnext(struct dsa_switch *ds, u16 *vid,
 		return -ENOENT;
 
 	mutex_lock(&ps->smi_mutex);
-	err = _mv88e6xxx_vtu_getnext(ds, *vid, &next);
+	err = _mv88e6xxx_vtu_vid_write(ds, *vid);
+	if (err)
+		goto unlock;
+
+	err = _mv88e6xxx_vtu_getnext(ds, &next);
+unlock:
 	mutex_unlock(&ps->smi_mutex);
 
 	if (err)