dsa: lan9303: Fix mapping between DSA port number and PHY address

The 'phy' parameter supplied to lan9303_phy_read/_write was sometimes a
DSA port number and sometimes a PHY address. This isn't a problem as
long as they are equal.  But if the external phy_addr_sel_strap pin is
wired to 'high', the PHY addresses change from 0-1-2 to 1-2-3 (CPU,
slave0, slave1).  In this case, lan9303_phy_read/_write must translate
between DSA port numbers and the corresponding PHY address.

Fixes: a129259 ("net: dsa: add new DSA switch driver for the SMSC-LAN9303")
Signed-off-by: Christian Eggers <ceggers@arri.de>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/20240703145718.19951-1-ceggers@arri.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: ceggers-arri

drivers/net/dsa/lan9303-core.c

@@ -1047,31 +1047,31 @@ static int lan9303_get_sset_count(struct dsa_switch *ds, int port, int sset)
 	return ARRAY_SIZE(lan9303_mib);
 }
 
-static int lan9303_phy_read(struct dsa_switch *ds, int phy, int regnum)
+static int lan9303_phy_read(struct dsa_switch *ds, int port, int regnum)
 {
 	struct lan9303 *chip = ds->priv;
 	int phy_base = chip->phy_addr_base;
 
-	if (phy == phy_base)
+	if (port == 0)
 		return lan9303_virt_phy_reg_read(chip, regnum);
-	if (phy > phy_base + 2)
+	if (port > 2)
 		return -ENODEV;
 
-	return chip->ops->phy_read(chip, phy, regnum);
+	return chip->ops->phy_read(chip, phy_base + port, regnum);
 }
 
-static int lan9303_phy_write(struct dsa_switch *ds, int phy, int regnum,
+static int lan9303_phy_write(struct dsa_switch *ds, int port, int regnum,
 			     u16 val)
 {
 	struct lan9303 *chip = ds->priv;
 	int phy_base = chip->phy_addr_base;
 
-	if (phy == phy_base)
+	if (port == 0)
 		return lan9303_virt_phy_reg_write(chip, regnum, val);
-	if (phy > phy_base + 2)
+	if (port > 2)
 		return -ENODEV;
 
-	return chip->ops->phy_write(chip, phy, regnum, val);
+	return chip->ops->phy_write(chip, phy_base + port, regnum, val);
 }
 
 static int lan9303_port_enable(struct dsa_switch *ds, int port,
@@ -1099,7 +1099,7 @@ static void lan9303_port_disable(struct dsa_switch *ds, int port)
 	vlan_vid_del(dsa_port_to_conduit(dp), htons(ETH_P_8021Q), port);
 
 	lan9303_disable_processing_port(chip, port);
-	lan9303_phy_write(ds, chip->phy_addr_base + port, MII_BMCR, BMCR_PDOWN);
+	lan9303_phy_write(ds, port, MII_BMCR, BMCR_PDOWN);
 }
 
 static int lan9303_port_bridge_join(struct dsa_switch *ds, int port,
@@ -1374,8 +1374,6 @@ static const struct dsa_switch_ops lan9303_switch_ops = {
 
 static int lan9303_register_switch(struct lan9303 *chip)
 {
-	int base;
-
 	chip->ds = devm_kzalloc(chip->dev, sizeof(*chip->ds), GFP_KERNEL);
 	if (!chip->ds)
 		return -ENOMEM;
@@ -1385,8 +1383,7 @@ static int lan9303_register_switch(struct lan9303 *chip)
 	chip->ds->priv = chip;
 	chip->ds->ops = &lan9303_switch_ops;
 	chip->ds->phylink_mac_ops = &lan9303_phylink_mac_ops;
-	base = chip->phy_addr_base;
-	chip->ds->phys_mii_mask = GENMASK(LAN9303_NUM_PORTS - 1 + base, base);
+	chip->ds->phys_mii_mask = GENMASK(LAN9303_NUM_PORTS - 1, 0);
 
 	return dsa_register_switch(chip->ds);
 }