net: dsa: lan9303: Set up trapping of IGMP to CPU port

IGMP packets should be trapped to the CPU port. The SW bridge knows
whether to forward to other ports.

With "IGMP snooping for local traffic" merged, IGMP trapping is also
required for stable IGMPv2 operation.

LAN9303 does not trap IGMP packets by default.

Enable IGMP trapping in lan9303_setup.

Signed-off-by: Egil Hjelmeland <privat@egil-hjelmeland.no>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/lan9303-core.c

@@ -153,6 +153,8 @@
 # define LAN9303_SWE_VLAN_UNTAG_PORT0 BIT(12)
 #define LAN9303_SWE_VLAN_CMD_STS 0x1810
 #define LAN9303_SWE_GLB_INGRESS_CFG 0x1840
+# define LAN9303_SWE_GLB_INGR_IGMP_TRAP BIT(7)
+# define LAN9303_SWE_GLB_INGR_IGMP_PORT(p) BIT(10 + p)
 #define LAN9303_SWE_PORT_STATE 0x1843
 # define LAN9303_SWE_PORT_STATE_FORWARDING_PORT2 (0)
 # define LAN9303_SWE_PORT_STATE_LEARNING_PORT2 BIT(5)
@@ -450,6 +452,21 @@ on_error:
 	return ret;
 }
 
+static int lan9303_write_switch_reg_mask(struct lan9303 *chip, u16 regnum,
+					 u32 val, u32 mask)
+{
+	int ret;
+	u32 reg;
+
+	ret = lan9303_read_switch_reg(chip, regnum, &reg);
+	if (ret)
+		return ret;
+
+	reg = (reg & ~mask) | val;
+
+	return lan9303_write_switch_reg(chip, regnum, reg);
+}
+
 static int lan9303_write_switch_port(struct lan9303 *chip, int port,
 				     u16 regnum, u32 val)
 {
@@ -905,6 +922,15 @@ static int lan9303_setup(struct dsa_switch *ds)
 	if (ret)
 		dev_err(chip->dev, "failed to re-enable switching %d\n", ret);
 
+	/* Trap IGMP to port 0 */
+	ret = lan9303_write_switch_reg_mask(chip, LAN9303_SWE_GLB_INGRESS_CFG,
+					    LAN9303_SWE_GLB_INGR_IGMP_TRAP |
+					    LAN9303_SWE_GLB_INGR_IGMP_PORT(0),
+					    LAN9303_SWE_GLB_INGR_IGMP_PORT(1) |
+					    LAN9303_SWE_GLB_INGR_IGMP_PORT(2));
+	if (ret)
+		dev_err(chip->dev, "failed to setup IGMP trap %d\n", ret);
+
 	return 0;
 }