net: macb: exclude software FCS from TX byte statistics

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Frames for which macb_pad_and_fcs() supplies the FCS have four FCS
bytes appended, and TX completion then accounts the grown skb->len.
tx_bytes is defined to exclude the FCS, so these frames are reported
four bytes too large.

Track only the number of FCS bytes appended in software, 0 or
ETH_FCS_LEN, and subtract that from skb->len at completion. skb->len
already reflects the padded length by then, so there is nothing else
to store. macb_pad_and_fcs() already returns 0 on every non-error
path. Return the FCS length from there instead, rather than
recomputing the same check in the caller. BQL stays on the padded
skb->len that netdev_tx_sent_queue() saw.

Fixes: 653e92a917 ("net: macb: add support for padding and fcs computation")
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Link: https://patch.msgid.link/20260831113128.1678674-1-nb@tipi-net.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Nicolai Buchwitz 2026-08-31 13:31:28 +02:00 • committed by Jakub Kicinski

parent debac3a20d

commit d85f521a9a

2 changed files with 16 additions and 8 deletions

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3

drivers/net/ethernet/cadence/macb.h

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21

drivers/net/ethernet/cadence/macb_main.c

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