[ Upstream commit 42fb3acf6826c6764ba79feb6e15229b43fd2f9f ]
JMS_MIN_SIZE is the full ethernet frame length, while mtu is just the
data payload size. Comparing these two meant that mtus between 1500 and
1518 did not trigger enabling jumbo frames.
So instead compare the set mtu ETH_DATA_LEN, which is equal to
JMS_MIN_SIZE - ETH_HLEN - ETH_FCS_LEN;
Also do a check that the requested mtu is actually greater than the
minimum length, else we do not need to enable jumbo frames.
In practice this only introduced a very small range of mtus that did not
work properly. Newer chips allow 2000 byte large frames by default, and
older chips allow 1536 bytes long, which is equivalent to an mtu of
1514. So effectivly only mtus of 1515~1517 were broken.
Fixes: 6ae5834b983a ("net: dsa: b53: add MTU configuration support")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ 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@gmail.com>
Signed-off-by: Martin Willi <martin@strongswan.org>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>