[AM335x] GEMAC - RMII Stuck at 10 Mbit/s Mode

AM335x Champs,

We've been able to get the GEMAC up and running using RMII.  However, we are stuck in 10Mbit/sec speeds, 1.1Mbyte/sec in fact, and are trying to acheive the 100Mbits speeds. We've included a scope shot of the REFCLK.  We are using the the LAN8720, which is the RMII version of the LAN8710 used on the Beaglebone and have boot strapped it to work in auto-negotiate mode.

 

Linux is indicating the following:

Inteface is up and auto-negotiating at 10Mbs

root@arm:~# ethtool eth0

Settings for eth0:

        Supported ports: [ TP MII ]

        Supported link modes:   10baseT/Half 10baseT/Full

        Supported pause frame use: Symmetric Receive-only

        Supports auto-negotiation: Yes

        Advertised link modes:  10baseT/Half 10baseT/Full

        Advertised pause frame use: Symmetric Receive-only

        Advertised auto-negotiation: Yes

       Speed: 10Mb/s

        Duplex: Full

        Port: MII

        PHYAD: 0

        Transceiver: external

        Auto-negotiation: on

        Current message level: 0x00000000 (0)

        Link detected: yes

Copying 100MB file:

data.bin   100%   51MB   1.1MB/s   00:47

Only 1 packet dropped, i.e. almost zero error rate

eth0      Link encap:Ethernet  HWaddr bc:6a:29:57:3e:dc

          inet addr:192.168.98.101  Bcast:192.168.98.255  Mask:255.255.255.0

          inet6 addr: fe80::be6a:29ff:fe57:3edc/64 Scope:Link

          UP BROADCAST RUNNING ALLMULTI MULTICAST  MTU:1500  Metric:1

          RX packets:48946 errors:0 dropped:1 overruns:0 frame:0

          TX packets:20632 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000

          RX bytes:57984084 (55.2 MiB)  TX bytes:1419359 (1.3 MiB)

Linux also shows interface operating at 10MBPs

root@arm:~# ifconfig eth0 up

[ 1855.735443] net eth0: CPSW phy found : id is : 0x7c0f1

[ 1855.753204] ADDRCONF(NETDEV_UP): eth0: link is not ready

root@arm:~# [ 1859.729888] PHY: 0:00 - Link is Up - 10/Full

[ 1859.734924] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready

 

Reading the PHY's configuration Register seems to indicate a form of 100MB/s was negotiated, see the 0111100000101101 value read from the phy basic status register.  The values for these bit fields are:

 

15 100BASE-T4

0 = no T4 ability

1 = T4 able

Value: 0b

 

14 100BASE-TX Full Duplex

0 = no TX full duplex ability

1 = TX with full duplex

Value: 1b

 

13 100BASE-TX Half Duplex

0 = no TX half duplex ability

1 = TX with half duplex

Value: 1b

 

12 10BASE-T Full Duplex

0 = no 10Mbps with full duplex ability

1 = 10Mbps with full duplex

Value: 1b

 

11 10BASE-T Half Duplex

0 = no 10Mbps with half duplex ability

1 = 10Mbps with half duplex

Value: 1b

 

10 100BASE-T2 Full Duplex

0 = PHY not able to perform full duplex 100BASE-T2

1 = PHY able to perform full duplex 100BASE-T2

Value: 0b

 

9 100BASE-T2 Half Duplex

0 = PHY not able to perform half duplex 100BASE-T2

1 = PHY able to perform half duplex 100BASE-T2

Value: 0b

 

8 Extended Status

0 = no extended status information in register 15

1 = extended status information in register 15

Value: 0b

5 Auto-Negotiate Complete

0 = auto-negotiate process not completed

1 = auto-negotiate process completed

Value: 0b

 

4 Remote Fault

1 = remote fault condition detected

0 = no remote fault

Value: 0b

 

3 Auto-Negotiate Ability

0 = unable to perform auto-negotiation function

1 = able to perform auto-negotiation function

Value: 1b

 

2 Link Status

0 = link is down

1 = link is up

Value: 0b

 

1 Jabber Detect

0 = no jabber condition detected

1 = jabber condition detected

Value: 0b

 

0 Extended Capabilities

0 = does not support extended capabilities registers

1 = supports extended capabilities registers

Value: 1b

 

So this indicates 100MB/s was negotiated, but not 100BASE-T2 Full Duplex. 

 

 

REFCLK Scope:

Link to LAN8720 Datasheet:

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