net: stmmac: size the RX buffers from the frame length, not the MTU

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When picking the buffsize to use based on the MTU, we shouldn't check
only the MTU value, but also :
 - ETH_HLEN for the L2 header,
 - up to 2 VLAN tags,
 - the FCS,

The default bufsize is 1536 bytes, which is enough to contain all the
above so this hasn't surfaced before, but the addition of NET_IP_ALIGN
to the start of buffer address tripped the Jumbo selftest, leading to
this discovery.

With that, we don't need the '>=' checks on the buffer len, we can use
more consistent comparison operators in stmmac_set_bfsize.

Fixes: 286a837217 ("stmmac: add CHAINED descriptor mode support (V4)")
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260917215339.2022523-7-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Maxime Chevallier 2026-09-17 23:53:37 +02:00 • committed by Jakub Kicinski

parent b42e701277

commit b8a26d46c0

1 changed files with 11 additions and 9 deletions

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drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

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