net: dsa: mv88e6xxx: read then write PVID

The port register 0x07 contains more options than just the default VID,
even though they are not used yet. So prefer a read then write operation
over a direct write.

This also allows to keep track of the change through dynamic debug.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 4 deletions

diff --git a/drivers/net/dsa/mv88e6xxx.c b/drivers/net/dsa/mv88e6xxx.c
index 3a58a8afe537..1aee42d1c5f2 100644
--- a/drivers/net/dsa/mv88e6xxx.c
+++ b/drivers/net/dsa/mv88e6xxx.c
@@ -1166,23 +1166,45 @@ int mv88e6xxx_port_stp_update(struct dsa_switch *ds, int port, u8 state)
         return 0;
 }
 
-static int _mv88e6xxx_port_pvid_get(struct dsa_switch *ds, int port, u16 *pvid)
+static int _mv88e6xxx_port_pvid(struct dsa_switch *ds, int port, u16 *new,
+                                u16 *old)
 {
+        u16 pvid;
         int ret;
 
         ret = _mv88e6xxx_reg_read(ds, REG_PORT(port), PORT_DEFAULT_VLAN);
         if (ret < 0)
                 return ret;
 
-        *pvid = ret & PORT_DEFAULT_VLAN_MASK;
+        pvid = ret & PORT_DEFAULT_VLAN_MASK;
+
+        if (new) {
+                ret &= ~PORT_DEFAULT_VLAN_MASK;
+                ret |= *new & PORT_DEFAULT_VLAN_MASK;
+
+                ret = _mv88e6xxx_reg_write(ds, REG_PORT(port),
+                                           PORT_DEFAULT_VLAN, ret);
+                if (ret < 0)
+                        return ret;
+
+                netdev_dbg(ds->ports[port], "DefaultVID %d (was %d)\n", *new,
+                           pvid);
+        }
+
+        if (old)
+                *old = pvid;
 
         return 0;
 }
 
+static int _mv88e6xxx_port_pvid_get(struct dsa_switch *ds, int port, u16 *pvid)
+{
+        return _mv88e6xxx_port_pvid(ds, port, NULL, pvid);
+}
+
 static int _mv88e6xxx_port_pvid_set(struct dsa_switch *ds, int port, u16 pvid)
 {
-        return _mv88e6xxx_reg_write(ds, REG_PORT(port), PORT_DEFAULT_VLAN,
-                                   pvid & PORT_DEFAULT_VLAN_MASK);
+        return _mv88e6xxx_port_pvid(ds, port, &pvid, NULL);
 }
 
 static int _mv88e6xxx_vtu_wait(struct dsa_switch *ds)