net: dsa: lantiq_gswip: fix order in .remove operation

Russell King pointed out that disabling the switch by clearing
GSWIP_MDIO_GLOB_ENABLE before calling dsa_unregister_switch() is
problematic, as it violates a Golden Rule of driver development to
always first unpublish userspace interfaces and then disable the
hardware.

Fix this, and also simplify the probe() function, by introducing a
dsa_switch_ops teardown() operation which takes care of clearing the
GSWIP_MDIO_GLOB_ENABLE bit.

Fixes: 14fceff ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
Suggested-by: "Russell King (Oracle)" <linux@armlinux.org.uk>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/4ebd72a29edc1e4059b9666a26a0bb5d906a829a.1765241054.git.daniel@makrotopia.org
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: dangowrt

drivers/net/dsa/lantiq/lantiq_gswip.c

@@ -444,9 +444,6 @@ static void gswip_remove(struct platform_device *pdev)
 	if (!priv)
 		return;
 
-	/* disable the switch */
-	gswip_disable_switch(priv);
-
 	dsa_unregister_switch(priv->ds);
 
 	for (i = 0; i < priv->num_gphy_fw; i++)

drivers/net/dsa/lantiq/lantiq_gswip_common.c

@@ -752,6 +752,13 @@ static int gswip_setup(struct dsa_switch *ds)
 	return 0;
 }
 
+static void gswip_teardown(struct dsa_switch *ds)
+{
+	struct gswip_priv *priv = ds->priv;
+
+	regmap_clear_bits(priv->mdio, GSWIP_MDIO_GLOB, GSWIP_MDIO_GLOB_ENABLE);
+}
+
 static enum dsa_tag_protocol gswip_get_tag_protocol(struct dsa_switch *ds,
 						    int port,
 						    enum dsa_tag_protocol mp)
@@ -1629,6 +1636,7 @@ static const struct phylink_mac_ops gswip_phylink_mac_ops = {
 static const struct dsa_switch_ops gswip_switch_ops = {
 	.get_tag_protocol	= gswip_get_tag_protocol,
 	.setup			= gswip_setup,
+	.teardown		= gswip_teardown,
 	.port_setup		= gswip_port_setup,
 	.port_enable		= gswip_port_enable,
 	.port_disable		= gswip_port_disable,
@@ -1718,15 +1726,14 @@ int gswip_probe_common(struct gswip_priv *priv, u32 version)
 
 	err = gswip_validate_cpu_port(priv->ds);
 	if (err)
-		goto disable_switch;
+		goto unregister_switch;
 
 	dev_info(priv->dev, "probed GSWIP version %lx mod %lx\n",
 		 GSWIP_VERSION_REV(version), GSWIP_VERSION_MOD(version));
 
 	return 0;
 
-disable_switch:
-	gswip_disable_switch(priv);
+unregister_switch:
 	dsa_unregister_switch(priv->ds);
 
 	return err;