net: dsa: microchip: ksz8795: Fix VLAN untagged flag change on deletion

commit af01754 upstream.

When a VLAN is deleted from a port, the flags in struct
switchdev_obj_port_vlan are always 0.  ksz8_port_vlan_del() copies the
BRIDGE_VLAN_INFO_UNTAGGED flag to the port's Tag Removal flag, and
therefore always clears it.

In case there are multiple VLANs configured as untagged on this port -
which seems useless, but is allowed - deleting one of them changes the
remaining VLANs to be tagged.

It's only ever necessary to change this flag when a VLAN is added to
the port, so leave it unchanged in ksz8_port_vlan_del().

Fixes: e66f840 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
[bwh: Backport to 5.10: adjust context]
Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/net/dsa/microchip/ksz8795.c

@@ -895,7 +895,6 @@ static void ksz8795_port_vlan_add(struct dsa_switch *ds, int port,
 static int ksz8795_port_vlan_del(struct dsa_switch *ds, int port,
 				 const struct switchdev_obj_port_vlan *vlan)
 {
-	bool untagged = vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED;
 	struct ksz_device *dev = ds->priv;
 	u16 data, vid, pvid;
 	u8 fid, member, valid;
@@ -904,8 +903,6 @@ static int ksz8795_port_vlan_del(struct dsa_switch *ds, int port,
 	ksz_pread16(dev, port, REG_PORT_CTRL_VID, &pvid);
 	pvid = pvid & 0xFFF;
 
-	ksz_port_cfg(dev, port, P_TAG_CTRL, PORT_REMOVE_TAG, untagged);
-
 	for (vid = vlan->vid_begin; vid <= vlan->vid_end; vid++) {
 		ksz8795_r_vlan_table(dev, vid, &data);
 		ksz8795_from_vlan(data, &fid, &member, &valid);