[LEDE-DEV] Devolo dLAN pro 500 Wireless+ and PLC (Power-line communication not Programmable logic controller)

[Denis 'GNUtoo' Carikli]

Hi,

I have a Devolo dLAN pro 500 Wireless+, which, has an "AR7400 PLC in PHY
mode" according to the following commit:
> 02984a6e09 ar71xx: add support for the devolo dLAN pro 500 Wireless+
If I understand well the code/platform-data below, it should appear on
eth0:
> /* GMAC0 is connected to a AR7400 PLC in PHY mode */
> ath79_init_mac(ath79_eth0_data.mac_addr, wifi_mac, 2);
> ath79_eth0_data.phy_if_mode = PHY_INTERFACE_MODE_RGMII;
> ath79_eth0_pll_data.pll_1000 = 0x0e000000;
> ath79_eth0_data.speed = SPEED_1000;
> ath79_eth0_data.duplex = DUPLEX_FULL;
> ath79_register_eth(0);

How can I use the powerline functionality?
- I've compiled an image with the plc-utils
- I find now way to talk to the AR7400: 
  - amptool finds nothing and exits:
  # amptool -i eth0 -Iar
  eth0 00:B0:52:00:00:01 Request Version Information
  eth0 00:B0:52:00:00:01 Fetch Device Attributes
  eth0 00:B0:52:00:00:01 Device Identity
  - Running plcID with the following command shows the same frame:
  # plcID -i eth0 -v

- I also tried removing eth0 from the br-lan bridge but the command
  line PLC identification tools mentioned above didn't have more
  success.

- According to blog posts like this one, the PLC should respond to
  PLC identification tools:
  http://www.fredericb.info/2016/02/powerline-plc-support-in-openwrt-for-d.html

- Should I look for the chip datasheet in order to understand in what
  state/mode it is in from its wiring and from the PCB pictures[1]?

References:
-----------
[1] Due to safety reasons, I don't want to open the device often, to
    limit the probability of fatal accidents. I however took pictures
    of its internals and, there might be two flash chips and two
    different kind of RAM chips.

Denis.