[PATCH stable 4.19] net: dsa: b53: Correct learning for standalone ports

[Florian Fainelli <f.fainelli@xxxxxxxxx>]

Standalone ports should not have learning enabled since all the frames
are always copied to the CPU port. This is particularly important in
case an user-facing port intentionally spoofs the CPU port's MAC
address. With learning enabled we would end up with the switch having
incorrectly learned the address of the CPU port which typically results
in a complete break down of network connectivity until the address
learned ages out and gets re-learned, from the correct port this time.

There was no control of the BR_LEARNING flag until upstream commit
4098ced4680a485c5953f60ac63dff19f3fb3d42 ("Merge branch 'brport-flags'")
which is why we default to enabling learning when the ports gets added
as a bridge member.

Fixes: 967dd82ffc52 ("net: dsa: b53: Add support for Broadcom RoboSwitch")
Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
---
 drivers/net/dsa/b53/b53_common.c | 19 +++++++++++++++++++
 drivers/net/dsa/b53/b53_regs.h   |  1 +
 drivers/net/dsa/bcm_sf2.c        |  5 -----
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 335ce1e84904..7eaeab65d39f 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -507,12 +507,27 @@ void b53_imp_vlan_setup(struct dsa_switch *ds, int cpu_port)
 }
 EXPORT_SYMBOL(b53_imp_vlan_setup);
 
+static void b53_port_set_learning(struct b53_device *dev, int port,
+				  bool learning)
+{
+	u16 reg;
+
+	b53_read16(dev, B53_CTRL_PAGE, B53_DIS_LEARNING, &reg);
+	if (learning)
+		reg &= ~BIT(port);
+	else
+		reg |= BIT(port);
+	b53_write16(dev, B53_CTRL_PAGE, B53_DIS_LEARNING, reg);
+}
+
 int b53_enable_port(struct dsa_switch *ds, int port, struct phy_device *phy)
 {
 	struct b53_device *dev = ds->priv;
 	unsigned int cpu_port = ds->ports[port].cpu_dp->index;
 	u16 pvlan;
 
+	b53_port_set_learning(dev, port, false);
+
 	/* Clear the Rx and Tx disable bits and set to no spanning tree */
 	b53_write8(dev, B53_CTRL_PAGE, B53_PORT_CTRL(port), 0);
 
@@ -620,6 +635,7 @@ static void b53_enable_cpu_port(struct b53_device *dev, int port)
 	b53_write8(dev, B53_CTRL_PAGE, B53_PORT_CTRL(port), port_ctrl);
 
 	b53_brcm_hdr_setup(dev->ds, port);
+	b53_port_set_learning(dev, port, false);
 }
 
 static void b53_enable_mib(struct b53_device *dev)
@@ -1517,6 +1533,8 @@ int b53_br_join(struct dsa_switch *ds, int port, struct net_device *br)
 	b53_write16(dev, B53_PVLAN_PAGE, B53_PVLAN_PORT_MASK(port), pvlan);
 	dev->ports[port].vlan_ctl_mask = pvlan;
 
+	b53_port_set_learning(dev, port, true);
+
 	return 0;
 }
 EXPORT_SYMBOL(b53_br_join);
@@ -1564,6 +1582,7 @@ void b53_br_leave(struct dsa_switch *ds, int port, struct net_device *br)
 		vl->untag |= BIT(port) | BIT(cpu_port);
 		b53_set_vlan_entry(dev, pvid, vl);
 	}
+	b53_port_set_learning(dev, port, false);
 }
 EXPORT_SYMBOL(b53_br_leave);
 
diff --git a/drivers/net/dsa/b53/b53_regs.h b/drivers/net/dsa/b53/b53_regs.h
index c90985c294a2..b2c539a42154 100644
--- a/drivers/net/dsa/b53/b53_regs.h
+++ b/drivers/net/dsa/b53/b53_regs.h
@@ -115,6 +115,7 @@
 #define B53_UC_FLOOD_MASK		0x32
 #define B53_MC_FLOOD_MASK		0x34
 #define B53_IPMC_FLOOD_MASK		0x36
+#define B53_DIS_LEARNING		0x3c
 
 /*
  * Override Ports 0-7 State on devices with xMII interfaces (8 bit)
diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index 613f03f9d9ec..e9fe3897bd9c 100644
--- a/drivers/net/dsa/bcm_sf2.c
+++ b/drivers/net/dsa/bcm_sf2.c
@@ -173,11 +173,6 @@ static int bcm_sf2_port_setup(struct dsa_switch *ds, int port,
 	reg &= ~P_TXQ_PSM_VDD(port);
 	core_writel(priv, reg, CORE_MEM_PSM_VDD_CTRL);
 
-	/* Enable learning */
-	reg = core_readl(priv, CORE_DIS_LEARN);
-	reg &= ~BIT(port);
-	core_writel(priv, reg, CORE_DIS_LEARN);
-
 	/* Enable Broadcom tags for that port if requested */
 	if (priv->brcm_tag_mask & BIT(port))
 		b53_brcm_hdr_setup(ds, port);
-- 
2.25.1