- 1 Configuration
- 2 Hardware
- 2.1 EMAC
- 2.2 GMAC
- 2.3 Phyceivers
- 2.4 Sun8i emac
- 3 Devices
Setting the MAC address
By default both EMAC and GMAC use random MAC addresses that change with each reboot, but this can be fixed.
The Bash script below will generate a unicast, locally administered, random MAC address. The first octet has bit 0 unset for unicast and bit 1 set for local administration so will be either X2, X6, Xa or Xe:
printf "%02x" $((RANDOM%256 & 254 | 2));hexdump -n 5 -e '""5/1 ":%02x""\n"' /dev/urandom
This MAC address can be loaded on each boot using one of the methods below to give a static MAC address.
For alternative sources of MAC addresses the FAQ 14.2.14. Where Can I Get a Valid MAC Address from? at the U-Boot website may help.
[dynamic] MAC = "XXXXXXXXXXXX"
the bootloader to append mac_addr=XX:XX:XX:XX:XX:XX
Through module options
ifconfig eth0 hw ether XX:XX:XX:XX:XX:XX
Allwinner's A10, A20 and F20 SoCs include a MAC unit called EMAC but it's available on very few devices, most notably the Mele A1000, A2000 and A100 HTPC and the Cubieboard. Due to driver similarities it's believed to be based on DM9000.
It has been discovered that the EMAC device (or its current Linux kernel driver) have a number of performance issues: slow RX performance (only 40-60 Mbit, compared to 90+ Mbit TX), active TX affecting RX rate way too much.
It seems that in some cases performance degrades only if the A10 device has been warm-rebooted prior to that; and speeds restore to immensely better levels after a full power-off/power-on cycle.
See the following discussions for details:
- Uploading affects Downloading. Ethernet performance issue?
- Something is still wrong with WEMAC
- Low ethernet speeds after reboot (a power cycle restores normal speeds)
- Slow network (receive, cable)
Mainline Kernel driver
The EMAC driver can be found under "Ethernet driver support", "Allwinner devices", "Allwinner A10 EMAC support". It was merged for kernel 3.11.
Allwinner's A20, A31/A31s and the A80 contain a MAC unit called GMAC ("Gigabit MAC"). The controller supports MII and RGMII modes. On the A20 it is pin compatible with the EMAC in MII mode. Also on A20 the manufacturer of the device in question can decide whether to use EMAC or GMAC. The controller is an early version of the Synopsys DWMAC (DesignWare MAC), with some hardware specific glue.
The SoC's GMAC is always combined with an external PHY, in most cases a RTL8211E/CL (the Lamobo R1 uses the Broadcom BCM53125 switch IC instead). Important: In this special mode the RTL8211 chip is just used as PHY and only responsible for layer 1 operations, since everything else happens inside the SoC's GMAC (therefore no RealTek drivers are needed and some functionality differs, e.g. no WoL possible).
For reliable Gigabit networking (1000Mbit operation), several sunxi devices require an important tweak that adjusts the relative timing of the clock and data signals to the PHY, in order to compensate for differing trace lengths on the PCB (details). Among others, this includes Banana Pi/Pro, Cubietruck, Lamobo R1, pcDuino3 Nano and Orange Pi/Mini. Recent mainline U-Boot uses CONFIG_GMAC_TX_DELAY to initialize these devices accordingly. If a necessary GMAC TX delay isn't set, then GBit Ethernet operation might be unreliable or won't work at all. 10/100 Mbit/sec negotiation is unaffected, so misconfigured devices could actually work (faster) when connected to a Fast Ethernet port instead of a GBit Ethernet port.
Mainline Kernel driver
DWMAC is supported by the stmmac driver ("Ethernet driver support", "STMicroelectronics devices", "STMicroelectronics 10/100/1000 Ethernet driver", "STMMAC Platform bus support"). Platform glue for sunxi was merged in 3.14. Device tree patches for supported A20 devices were merged in 3.15.
The Broadcom BCM53125 is an integrated 7-port Gbit Ethernet switch IC that can be configured to act as a PHY on one port interconnecting the SoC with all wired Ethernet ports. It works with OpenWrt's b53-mdio driver, and the capability to route packets between different ports is based on VLANs and assigning them to virtual interfaces. At least the implementation on the Lamobo R1 suffers from less possible throughput compared to A20's GMAC working together with RTL8211 as PHY.
The ICplus IP101A is a RMII 10/100 Ethernet PHY.
The ICplus IP101GA is a RMII 10/100 Ethernet PHY.
The KSZ9031 is a gigabit ethernet PHY.
It may require adjusting RX or TX delays, depending on PCB wiring of each board. According to git commit notes for the linux driver, TX delay can be 0 - 1.38ns and RX delay can be 0 - 2.58ns.
The Realtek RTL8201CP is a MII mode 10/100 Ethernet PHY. It is very very common and supported by just about any kernel out there, either with the generic phy driver or the realtek one.
The Realtek RTL8211E is a RGMII 10/100/1000 Ethernet PHY, which is gigabit capable. It is commonly paired with GMAC for gigabit speeds. Generic PHY support is enough to make it work.
The RTL8211 is known to have trouble connecting to certain types of devices. The problem is caused by an instable PLL when configured as master. A fix has been applied to u-boot. http://lists.denx.de/pipermail/u-boot/2016-March/249734.html
The following devices all come with an ethernet port.