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[Kleber Sacilotto de Souza <kleber.souza@xxxxxxxxxxxxx>]

** Also affects: linux-raspi2 (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux-raspi2 (Ubuntu Xenial)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1798578

Title:
  RaspberryPi3+: can't set mac address from device tree

Status in linux-raspi2 package in Ubuntu:
  Invalid
Status in linux-raspi2 source package in Xenial:
  In Progress

Bug description:
  Impact:

  The RaspberryPi3+ board came with an usb's to ethernet lan78xx nic
  adapter - thhis chip has no external eeprom, nor internal
  preprogrammed mac address and as such, after every reboot, it
  generates a random new ethernet mac address.

  Supposedly, the lan78xx driver is able to read its mac address from
  the device tree passed to the kernel (see d093067 "lan78xx: Read MAC
  address from DT if present"), making it possible to have
  reproducible/fixed mac addresses, but unfortunately this feature isn't
  working in our Xenial/raspi2 kernel (while it's working fine in
  Bionc/raspi2).

  After some debugging i found that the usb_net struct backing the
  lan78xx driver, had no clue about the dt node it was associated,
  making this piece of code constantly evaluates to NULL:

  static void lan78xx_init_mac_address(struct lan78xx_net *dev)
  ...
  mac_addr = of_get_mac_address(dev->udev->dev.of_node);
  ...

  There "of_node" was always NULL.

  After more debugging, i found that the feature to bind usb_net devices
  and device tree nodes was introduced in the Linux 4.6 cycle, and as
  such Xenial didn't have it.

  Fix:

  Apply the patch and recompile

  How to test:

  Upon boot of the RaspberryPi3+ board (and after the dtb has been
  loaded into memory), stop at the uboot prompt and check the usbeether
  device node:

  U-Boot> fdt print /soc/usb/usb1@1/usb1_1@1/usbether@1
  usbether@1 {
          local-mac-address = [b8 27 eb ce 07 ba];
          compatible = "usb424,7800";
          reg = <0x00000001>;
          microchip,eee-enabled;
          microchip,tx-lpi-timer = <0x00000258>;
          phandle = <0x00000024>;
  };

  the "local-mac-address" has been filled by the Broadcom bootloader,
  and contains the lan78xx's mac address.

  Then proceed with the boot routine, readh the user prompt, and check
  eth0's mac address:

  $ ifconfig eth0 | grep HWaddr
  eth0      Link encap:Ethernet  HWaddr b8:27:eb:ce:07:ba  

  If it's the same as above, then the fix worked.

  Regression:

  The patch itself has been upstream since v4.6-rc1, and it changes a
  very small portion of code, so i'll say it's regression potential is
  very low / none.

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