Add flow control support. The functionality was tested on AR9331 SoC and
confirmed by iperf3 results and HW counters exported over ethtool.
Following test configurations was used:
iMX6S receiver <--- TL-SG1005D switch <---- AR9331 sender
The switch is supporting symmytric flow control:
Settings for eth0:
Supported ports: [ MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supported pause frame use: Symmetric Receive-only
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Link partner advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
--->> Link partner advertised pause frame use: Symmetric
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported
Speed: 100Mb/s
Duplex: Full
Auto-negotiation: on
Port: MII
PHYAD: 4
Transceiver: external
Link detected: yes
The iMX6S system was configured to 10Mbit, to let the switch use flow
control:
- ethtool -s eth0 speed 10
With flow control disabled on AR9331:
- ethtool -A eth0 rx off tx off
- iperf3 -u -c 172.17.0.1 -b100M -l1472 -t10
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 66.2 MBytes 55.5 Mbits/sec 0.000 ms 0/47155 (0%) sender
[ 5] 0.00-10.04 sec 11.5 MBytes 9.57 Mbits/sec 1.309 ms 38986/47146 (83%) receiver
With flow control enabled on AR9331:
- ethtool -A eth0 rx on tx on
- iperf3 -u -c 172.17.0.1 -b100M -l1472 -t10
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 15.1 MBytes 12.6 Mbits/sec 0.000 ms 0/10727 (0%) sender
[ 5] 0.00-10.05 sec 11.5 MBytes 9.57 Mbits/sec 1.371 ms 2525/10689 (24%) receiver
Similar results are get in opposite direction by introducing extra CPU
load on AR9331:
- chrt 40 dd if=/dev/zero of=/dev/null &
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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