staging: dpaa2-switch: make sure that the VLAN is not already configured

When in the PREPARE state of a switchdev transaction, check if the
requested VLAN is not already configured on the switch port. This keeps
us from getting into a WARNING as below.

[ 1389.683296] dpaa2_ethsw dpsw.0 eth0: VLAN 2 already configured
[ 1389.689125] ------------[ cut here ]------------
[ 1389.694084] eth0: Commit of object (id=1) failed.
[ 1389.698863] WARNING: CPU: 0 PID: 613 at net/switchdev/switchdev.c:277 switchdev_port_obj_add_now+0xcc/0x110
[ 1389.708589] Modules linked in:
[ 1389.711634] CPU: 0 PID: 613 Comm: bridge Not tainted 5.9.0-rc2-next-20200828-00112-g7172078477c5 #59
[ 1389.720753] Hardware name: NXP Layerscape LX2160ARDB (DT)
[ 1389.726139] pstate: 40000005 (nZcv daif -PAN -UAO BTYPE=--)
[ 1389.731698] pc : switchdev_port_obj_add_now+0xcc/0x110
[ 1389.736824] lr : switchdev_port_obj_add_now+0xcc/0x110
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20201119165017.806696-3-ciorneiioana@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-dpaa2/ethsw/ethsw.c

@@ -984,10 +984,17 @@ static int dpaa2_switch_port_vlans_add(struct net_device *netdev,
 	int vid, err = 0, new_vlans = 0;
 
 	if (switchdev_trans_ph_prepare(trans)) {
-		for (vid = vlan->vid_begin; vid <= vlan->vid_end; vid++)
+		for (vid = vlan->vid_begin; vid <= vlan->vid_end; vid++) {
 			if (!port_priv->ethsw_data->vlans[vid])
 				new_vlans++;
 
+			/* Make sure that the VLAN is not already configured
+			 * on the switch port
+			 */
+			if (port_priv->vlans[vid] & ETHSW_VLAN_MEMBER)
+				return -EEXIST;
+		}
+
 		/* Check if there is space for a new VLAN */
 		err = dpsw_get_attributes(ethsw->mc_io, 0, ethsw->dpsw_handle,
 					  &ethsw->sw_attr);