Merge branch 'fix-large-frames-in-the-gemini-ethernet-driver'

Merge branch 'fix-large-frames-in-the-gemini-ethernet-driver'

Linus Walleij says:

====================
Fix large frames in the Gemini ethernet driver

This is the result of a bug hunt for a problem with the
RTL8366RB DSA switch leading me wrong all over the place.

I am indebted to Vladimir Oltean who as usual pointed
out where the real problem was, many thanks!

Tryig to actually use big ("jumbo") frames on this
hardware uncovered the real bugs. Then I tested it on
the DSA switch and it indeed fixes the issue.

To make sure it also works fine with big frames on
non-DSA devices I also copied a large video file over
scp to a device with maximum frame size, the data
was transported in large TCP packets ending up in
0x7ff sized frames using software checksumming at
~2.0 MB/s.

If I set down the MTU to the standard 1500 bytes so
that hardware checksumming is used, the scp transfer
of the same file was slightly lower, ~1.8-1.9 MB/s.

Despite this not being the best test it shows that
we can now stress the hardware with large frames
and that software checksum works fine.

v3: https://lore.kernel.org/r/20231107-gemini-largeframe-fix-v3-0-e3803c080b75@linaro.org
v2: https://lore.kernel.org/r/20231105-gemini-largeframe-fix-v2-0-cd3a5aa6c496@linaro.org
v1: https://lore.kernel.org/r/20231104-gemini-largeframe-fix-v1-0-9c5513f22f33@linaro.org
====================

Link: https://lore.kernel.org/r/20231109-gemini-largeframe-fix-v4-0-6e611528db08@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>