diff options
| author | Frank Li <Frank.Li@nxp.com> | 2023-05-18 11:49:45 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-05-29 15:23:59 +0100 |
| commit | dbe678f6192f27879ac9ff6bc7a1036aad85aae9 (patch) | |
| tree | 7f39a65393d56702b30f71a9744e213d1dbf36a8 /drivers/usb/gadget/function/f_fs.c | |
| parent | 7877cb91f1081754a1487c144d85dc0d2e2e7fc4 (diff) | |
usb: cdns3: fix NCM gadget RX speed 20x slow than expection at iMX8QM
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: 7733f6c32e36 ("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>
Diffstat (limited to 'drivers/usb/gadget/function/f_fs.c')
0 files changed, 0 insertions, 0 deletions