This is a note to let you know that I've just added the patch titled
net: dsa: b53: Limit chip-wide jumbo frame config to CPU ports
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-dsa-b53-limit-chip-wide-jumbo-frame-config-to-cp.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b34545a9afd807e5998d42f7d3a0e9c62b7fc694
Author: Martin Willi <martin@xxxxxxxxxxxxxx>
Date: Wed Jul 17 11:08:20 2024 +0200
net: dsa: b53: Limit chip-wide jumbo frame config to CPU ports
[ Upstream commit c5118072e228e7e4385fc5ac46b2e31cf6c4f2d3 ]
Broadcom switches supported by the b53 driver use a chip-wide jumbo frame
configuration. In the commit referenced with the Fixes tag, the setting
is applied just for the last port changing its MTU.
While configuring CPU ports accounts for tagger overhead, user ports do
not. When setting the MTU for a user port, the chip-wide setting is
reduced to not include the tagger overhead, resulting in an potentially
insufficient chip-wide maximum frame size for the CPU port.
As, by design, the CPU port MTU is adjusted for any user port change,
apply the chip-wide setting only for CPU ports. This aligns the driver
to the behavior of other switch drivers.
Fixes: 6ae5834b983a ("net: dsa: b53: add MTU configuration support")
Suggested-by: Vladimir Oltean <olteanv@xxxxxxxxx>
Signed-off-by: Martin Willi <martin@xxxxxxxxxxxxxx>
Reviewed-by: Vladimir Oltean <olteanv@xxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 604f541126654..e23f184ffdda7 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -2223,6 +2223,9 @@ static int b53_change_mtu(struct dsa_switch *ds, int port, int mtu)
if (is5325(dev) || is5365(dev))
return -EOPNOTSUPP;
+ if (!dsa_is_cpu_port(ds, port))
+ return 0;
+
enable_jumbo = (mtu >= JMS_MIN_SIZE);
allow_10_100 = (dev->chip_id == BCM583XX_DEVICE_ID);
