net: dsa: microchip: ksz8795: Fix PVID tag insertion

ksz8795 has never actually enabled PVID tag insertion, and it also
programmed the PVID incorrectly.  To fix this:

* Allow tag insertion to be controlled per ingress port.  On most
  chips, set bit 2 in Global Control 19.  On KSZ88x3 this control
  flag doesn't exist.

* When adding a PVID:
  - Set the appropriate register bits to enable tag insertion on
    egress at every other port if this was the packet's ingress port.
  - Mask *out* the VID from the default tag, before or-ing in the new
    PVID.

* When removing a PVID:
  - Clear the same control bits to disable tag insertion.
  - Don't update the default tag.  This wasn't doing anything useful.

Fixes: e66f840 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
Signed-off-by: Ben Hutchings <ben.hutchings@mind.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz8795.c

@@ -1124,6 +1124,16 @@ static int ksz8_port_vlan_filtering(struct dsa_switch *ds, int port, bool flag,
 	return 0;
 }
 
+static void ksz8_port_enable_pvid(struct ksz_device *dev, int port, bool state)
+{
+	if (ksz_is_ksz88x3(dev)) {
+		ksz_cfg(dev, REG_SW_INSERT_SRC_PVID,
+			0x03 << (4 - 2 * port), state);
+	} else {
+		ksz_pwrite8(dev, port, REG_PORT_CTRL_12, state ? 0x0f : 0x00);
+	}
+}
+
 static int ksz8_port_vlan_add(struct dsa_switch *ds, int port,
 			      const struct switchdev_obj_port_vlan *vlan,
 			      struct netlink_ext_ack *extack)
@@ -1160,9 +1170,11 @@ static int ksz8_port_vlan_add(struct dsa_switch *ds, int port,
 		u16 vid;
 
 		ksz_pread16(dev, port, REG_PORT_CTRL_VID, &vid);
-		vid &= 0xfff;
+		vid &= ~VLAN_VID_MASK;
 		vid |= new_pvid;
 		ksz_pwrite16(dev, port, REG_PORT_CTRL_VID, vid);
+
+		ksz8_port_enable_pvid(dev, port, true);
 	}
 
 	return 0;
@@ -1173,7 +1185,7 @@ static int ksz8_port_vlan_del(struct dsa_switch *ds, int port,
 {
 	bool untagged = vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED;
 	struct ksz_device *dev = ds->priv;
-	u16 data, pvid, new_pvid = 0;
+	u16 data, pvid;
 	u8 fid, member, valid;
 
 	if (ksz_is_ksz88x3(dev))
@@ -1195,14 +1207,11 @@ static int ksz8_port_vlan_del(struct dsa_switch *ds, int port,
 		valid = 0;
 	}
 
-	if (pvid == vlan->vid)
-		new_pvid = 1;
-
 	ksz8_to_vlan(dev, fid, member, valid, &data);
 	ksz8_w_vlan_table(dev, vlan->vid, data);
 
-	if (new_pvid != pvid)
-		ksz_pwrite16(dev, port, REG_PORT_CTRL_VID, pvid);
+	if (pvid == vlan->vid)
+		ksz8_port_enable_pvid(dev, port, false);
 
 	return 0;
 }
@@ -1435,6 +1444,9 @@ static int ksz8_setup(struct dsa_switch *ds)
 
 	ksz_cfg(dev, S_MIRROR_CTRL, SW_MIRROR_RX_TX, false);
 
+	if (!ksz_is_ksz88x3(dev))
+		ksz_cfg(dev, REG_SW_CTRL_19, SW_INS_TAG_ENABLE, true);
+
 	/* set broadcast storm protection 10% rate */
 	regmap_update_bits(dev->regmap[1], S_REPLACE_VID_CTRL,
 			   BROADCAST_STORM_RATE,

drivers/net/dsa/microchip/ksz8795_reg.h

@@ -631,6 +631,10 @@
 #define REG_PORT_4_OUT_RATE_3		0xEE
 #define REG_PORT_5_OUT_RATE_3		0xFE
 
+/* 88x3 specific */
+
+#define REG_SW_INSERT_SRC_PVID		0xC2
+
 /* PME */
 
 #define SW_PME_OUTPUT_ENABLE		BIT(1)