IMX6Q Enet Cannot Reach 1000M

javen — Fri, 05 Feb 2016 02:20:22 GMT

Can anyone help me? in my MX6Q custom board based on MX6QSD(imx_3.0.35_4.1.0), our 1GB RGMII ethernet can only work at speed 495Mbits/sec,

is this normal ? Which configuration will affect the speed？

=============================================

iperf -c 192.168.122.125 -u -b 800M -t 10 -l 1000

------------------------------------------------------------

Client connecting to 192.168.122.125, UDP port 5001

Sending 1000 byte datagrams

UDP buffer size: 208 KByte (default)

------------------------------------------------------------

[ 3] local 192.168.122.6 port 45130 connected with 192.168.122.125 port 5001

[ ID] Interval Transfer Bandwidth

[ 3] 0.0-10.0 sec 590 MBytes 495 Mbits/sec

[ 3] Sent 618437 datagrams

[ 3] WARNING: did not receive ack of last datagram after 10 tries.

Re: IMX6Q Enet Cannot Reach 1000M

gary_bisson — Fri, 05 Feb 2016 09:50:31 GMT

Hi Javen,

This is a known issue. Please read the "Chip Errata for the i.MX 6" and look for the ERR004512:

The theoretical maximum performance of 1 Gbps ENET is limited to 470 Mbps.
Limitation of ENET throughput to around 400 Mbps. ENET remains fully compatible to 1Gb standard in terms of protocol and physical signaling. If the TX and RX peak data rate is higher than 400 Mbps, there is a risk of ENET RX FIFO overrun.
There is no workaround for the throughput limitation.

Regards,

Gary