linux-kernel - [PATCH net] net: dsa: b53: fix ageing time for BCM53101

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Message-ID: <20250823090617.15329-1-jonas.gorski@gmail.com>
Date: Sat, 23 Aug 2025 11:06:16 +0200
From: Jonas Gorski <jonas.gorski@...il.com>
To: Florian Fainelli <florian.fainelli@...adcom.com>,
	Andrew Lunn <andrew@...n.ch>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Jonas Gorski <jonas.gorski@...il.com>
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net] net: dsa: b53: fix ageing time for BCM53101

For some reason Broadcom decided that BCM53101 uses 0.5s increments for
the ageing time register, but kept the field width the same [1]. Due to
this, the actual ageing time was always half of what was configured.

Fix this by adapting the limits and value calculation for BCM53101.

[1] https://github.com/Broadcom-Network-Switching-Software/OpenMDK/blob/master/cdk/PKG/chip/bcm53101/bcm53101_a0_defs.h#L28966

Fixes: e39d14a760c0 ("net: dsa: b53: implement setting ageing time")
Signed-off-by: Jonas Gorski <jonas.gorski@...il.com>
---
Lacking matching hardware, this is only run-tested on non-matching
(BCM53115).

 drivers/net/dsa/b53/b53_common.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 829b1f087e9e..b85ca17e8fdd 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -1273,9 +1273,16 @@ static int b53_setup(struct dsa_switch *ds)
 	 */
 	ds->untag_vlan_aware_bridge_pvid = true;
 
-	/* Ageing time is set in seconds */
-	ds->ageing_time_min = 1 * 1000;
-	ds->ageing_time_max = AGE_TIME_MAX * 1000;
+
+	if (dev->chip_id == BCM53101_DEVICE_ID) {
+		/* BCM53101 uses 0.5 second increments */
+		ds->ageing_time_min = 1 * 500;
+		ds->ageing_time_max = AGE_TIME_MAX * 500;
+	} else {
+		/* Everything else uses 1 second increments */
+		ds->ageing_time_min = 1 * 1000;
+		ds->ageing_time_max = AGE_TIME_MAX * 1000;
+	}
 
 	ret = b53_reset_switch(dev);
 	if (ret) {
@@ -2559,7 +2566,10 @@ int b53_set_ageing_time(struct dsa_switch *ds, unsigned int msecs)
 	else
 		reg = B53_AGING_TIME_CONTROL;
 
-	atc = DIV_ROUND_CLOSEST(msecs, 1000);
+	if (dev->chip_id == BCM53101_DEVICE_ID)
+		atc = DIV_ROUND_CLOSEST(msecs, 500);
+	else
+		atc = DIV_ROUND_CLOSEST(msecs, 1000);
 
 	if (!is5325(dev) && !is5365(dev))
 		atc |= AGE_CHANGE;

base-commit: ec79003c5f9d2c7f9576fc69b8dbda80305cbe3a
-- 
2.43.0