[PATCH net v2] net: dsa: b53: fix ageing time for BCM53101

[PATCH net v2] net: dsa: b53: fix ageing time for BCM53101

[Jonas Gorski]

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.

So far it looks like this is the only chip with the increased tick
speed:

$ grep -l -r "Specifies the aging time in 0.5 seconds" cdk/PKG/chip | sort
cdk/PKG/chip/bcm53101/bcm53101_a0_defs.h

$ grep -l -r "Specifies the aging time in seconds" cdk/PKG/chip | sort
cdk/PKG/chip/bcm53010/bcm53010_a0_defs.h
cdk/PKG/chip/bcm53020/bcm53020_a0_defs.h
cdk/PKG/chip/bcm53084/bcm53084_a0_defs.h
cdk/PKG/chip/bcm53115/bcm53115_a0_defs.h
cdk/PKG/chip/bcm53118/bcm53118_a0_defs.h
cdk/PKG/chip/bcm53125/bcm53125_a0_defs.h
cdk/PKG/chip/bcm53128/bcm53128_a0_defs.h
cdk/PKG/chip/bcm53134/bcm53134_a0_defs.h
cdk/PKG/chip/bcm53242/bcm53242_a0_defs.h
cdk/PKG/chip/bcm53262/bcm53262_a0_defs.h
cdk/PKG/chip/bcm53280/bcm53280_a0_defs.h
cdk/PKG/chip/bcm53280/bcm53280_b0_defs.h
cdk/PKG/chip/bcm53600/bcm53600_a0_defs.h
cdk/PKG/chip/bcm89500/bcm89500_a0_defs.h

[1] https://github.com/Broadcom/OpenMDK/blob/a5d3fc9b12af3eeb68f2ca0ce7ec4056cd14d6c2/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@gmail.com>
---
v1 -> v2:
* Updated github URL to point to fixed commit
* added grep output for tick speed to commit message
* dropped extra empty line added at the start in b53_setup()

 drivers/net/dsa/b53/b53_common.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 829b1f087e9e..2f846381d5a7 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -1273,9 +1273,15 @@ 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 +2565,10 @@ 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: 157cf360c4a8751f7f511a71cc3a283b5d27f889
-- 
2.43.0

Re: [PATCH net v2] net: dsa: b53: fix ageing time for BCM53101

[Florian Fainelli]

On 9/5/25 05:45, Jonas Gorski wrote:
> 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.
> 
> So far it looks like this is the only chip with the increased tick
> speed:
> 
> $ grep -l -r "Specifies the aging time in 0.5 seconds" cdk/PKG/chip | sort
> cdk/PKG/chip/bcm53101/bcm53101_a0_defs.h
> 
> $ grep -l -r "Specifies the aging time in seconds" cdk/PKG/chip | sort
> cdk/PKG/chip/bcm53010/bcm53010_a0_defs.h
> cdk/PKG/chip/bcm53020/bcm53020_a0_defs.h
> cdk/PKG/chip/bcm53084/bcm53084_a0_defs.h
> cdk/PKG/chip/bcm53115/bcm53115_a0_defs.h
> cdk/PKG/chip/bcm53118/bcm53118_a0_defs.h
> cdk/PKG/chip/bcm53125/bcm53125_a0_defs.h
> cdk/PKG/chip/bcm53128/bcm53128_a0_defs.h
> cdk/PKG/chip/bcm53134/bcm53134_a0_defs.h
> cdk/PKG/chip/bcm53242/bcm53242_a0_defs.h
> cdk/PKG/chip/bcm53262/bcm53262_a0_defs.h
> cdk/PKG/chip/bcm53280/bcm53280_a0_defs.h
> cdk/PKG/chip/bcm53280/bcm53280_b0_defs.h
> cdk/PKG/chip/bcm53600/bcm53600_a0_defs.h
> cdk/PKG/chip/bcm89500/bcm89500_a0_defs.h
> 
> [1] https://github.com/Broadcom/OpenMDK/blob/a5d3fc9b12af3eeb68f2ca0ce7ec4056cd14d6c2/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@gmail.com>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
Florian

Re: [PATCH net v2] net: dsa: b53: fix ageing time for BCM53101

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri,  5 Sep 2025 14:45:07 +0200 you wrote:
> 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.
> 
> So far it looks like this is the only chip with the increased tick
> speed:
> 
> [...]

Here is the summary with links:
  - [net,v2] net: dsa: b53: fix ageing time for BCM53101
    https://git.kernel.org/netdev/net/c/674b34c4c770

You are awesome, thank you!
-- 
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