usb: cdns3: fix NCM gadget RX speed 20x slow than expection at iMX8QM

stable inclusion
from stable-v5.10.192
commit 3e2b5d66e9266c32d5d92d13636f1b5ae5315c06
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I933RF

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3e2b5d66e9266c32d5d92d13636f1b5ae5315c06



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[ Upstream commit dbe678f6 ]

At iMX8QM platform, enable NCM gadget and run 'iperf3 -s'.
At host, run 'iperf3 -V -c fe80::6863:98ff:feef:3e0%enxc6e147509498'

[  5]   0.00-1.00   sec  1.55 MBytes  13.0 Mbits/sec   90   4.18 KBytes
[  5]   1.00-2.00   sec  1.44 MBytes  12.0 Mbits/sec   75   4.18 KBytes
[  5]   2.00-3.00   sec  1.48 MBytes  12.4 Mbits/sec   75   4.18 KBytes

Expected speed should be bigger than 300Mbits/sec.

The root cause of this performance drop was found to be data corruption
happening at 4K borders in some Ethernet packets, leading to TCP
checksum errors. This corruption occurs from the position
(4K - (address & 0x7F)) to 4K. The u_ether function's allocation of
skb_buff reserves 64B, meaning all RX addresses resemble 0xXXXX0040.

Force trb_burst_size to 16 can fix this problem.

Cc: stable@vger.kernel.org
Fixes: 7733f6c3 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20230518154946.3666662-1-Frank.Li@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>