MT7623 Ethernet TX performance regression

[David Woodhouse]

Hi,

In 5.4 and 5.8.0-rc6+ kernels I see awful TX performance from the
Ethernet on (at least) MT7623 boards. It's been reported on a Banana Pi
R2, as well as UniElec U7623.

Using iperf3, receiving is fine:

[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   112 MBytes   942 Mbits/sec                  
[  5]   1.00-2.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   2.00-3.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   3.00-4.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   4.00-5.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   5.00-6.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   6.00-7.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   7.00-8.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   8.00-9.00   sec   112 MBytes   941 Mbits/sec                  
[  5]   9.00-10.00  sec   112 MBytes   941 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.10 GBytes   943 Mbits/sec    0             sender
[  5]   0.00-10.00  sec  1.10 GBytes   941 Mbits/sec                  receiver

Transmit, on the other hand, is fairly much completely hosed:

[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   212 KBytes  1.74 Mbits/sec   36   2.79 KBytes       
[  5]   1.00-2.00   sec   665 KBytes  5.45 Mbits/sec   66   1.39 KBytes       
[  5]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec   14   2.79 KBytes       
[  5]   3.00-4.00   sec   126 KBytes  1.03 Mbits/sec   10   2.79 KBytes       
[  5]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec    9   2.79 KBytes       
[  5]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec    7   1.39 KBytes       
[  5]   6.00-7.00   sec   251 KBytes  2.06 Mbits/sec   26   2.79 KBytes       
[  5]   7.00-8.00   sec   126 KBytes  1.03 Mbits/sec   22   1.39 KBytes       
[  5]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec    2   1.39 KBytes       
[  5]   9.00-10.00  sec   126 KBytes  1.03 Mbits/sec   15   2.79 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.47 MBytes  1.23 Mbits/sec  207             sender
[  5]   0.00-10.00  sec  1.26 MBytes  1.06 Mbits/sec                  receiver

This is seen with the OpenWrt 5.4 kernel, and also with a clean current
upstream 5.8.0-rc6 (with just one patch from
https://git.openwrt.org/?p=openwrt/openwrt.git;a=commitdiff;h=36105880ee5
without which it doesn't boot at all).

The previous kernel that I have running on these boards is 4.14, which
does give me close to 1Gb/s in both directions as it should.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 5174 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-mediatek/attachments/20200723/bcefe33e/attachment.bin>