net: dsa: b53: Fix calculating number of switch ports

BugLink: https://bugs.launchpad.net/bugs/1946802
[ Upstream commit cdb067d31c0fe4cce98b9d15f1f2ef525acaa094 ]

It isn't true that CPU port is always the last one. Switches BCM5301x
have 9 ports (port 6 being inactive) and they use port 5 as CPU by
default (depending on design some other may be CPU ports too).

A more reliable way of determining number of ports is to check for the
last set bit in the "enabled_ports" bitfield.

This fixes b53 internal state, it will allow providing accurate info to
the DSA and is required to fix BCM5301x support.

Fixes: 967dd82ffc52 ("net: dsa: b53: Add support for Broadcom RoboSwitch")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index e78b683f73052775f31c8ac4bb18da7753c5e48f..825d840cdb8c3bc1d052c20513a79622ec9a09b5 100644 (file)
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -2353,9 +2353,8 @@ static int b53_switch_init(struct b53_device *dev)
                        dev->cpu_port = 5;
        }
 
-       /* cpu port is always last */
-       dev->num_ports = dev->cpu_port + 1;
        dev->enabled_ports |= BIT(dev->cpu_port);
+       dev->num_ports = fls(dev->enabled_ports);
 
        /* Include non standard CPU port built-in PHYs to be probed */
        if (is539x(dev) || is531x5(dev)) {