linux-kernel - [PATCH 5.4 255/260] net: dsa: b53: Fix calculating number of switch ports

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Date:   Mon, 20 Sep 2021 18:44:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rafał Miłecki <rafal@...ecki.pl>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 255/260] net: dsa: b53: Fix calculating number of switch ports

From: Rafał Miłecki <rafal@...ecki.pl>

[ 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@...ecki.pl>
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/dsa/b53/b53_common.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index e78b683f7305..825d840cdb8c 100644
--- 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)) {
-- 
2.30.2