EthernetDoesNotWorkInLinux < DULG

%SECTION0{name=EthernetDoesNotWorkInLinux}% Ethernet does not work in Linux

   Question:: Ethernet does not work on my board. But everything is fine
    when I use the ethernet interface in
    U-Boot (for example by performing a TFTP download).
    This is a bug in U-Boot, right?

   Answer:: No. It's a bug in the Linux ethernet driver.
    %BR% %BR%
    In some cases the Linux driver fails to set the MAC address.
    That's a buggy driver then - Linux ethernet drivers are supposed to
    read the MAC address at startup.
    On ->open, they are supposed to reprogram the MAC address back into the
    chip (but not the EEPROM, if any) whether or not the address has been changed.
    %BR% %BR%
    In general, a Linux driver shall
    not make any assumptions about any initialization being done (or not
    done) by a boot loader; instead, that driver is responsible
    for performing all of the necessary initialization itself.
    %BR% %BR%
    And U-Boot shall not touch any hardware it does not access itself.
    If you don't use the ethernet interface in U-Boot, it won't be
    initialized by U-Boot.
    %BR% %BR%
    A pretty extensive discussion of this issue can be found in
    the thread *ATAG for MAC address* on the ARM Linux mailing list.
    [[http://lists.arm.linux.org.uk/lurker/message/20040706.101716.74b8122e.en.html][archive 1]]
    [[http://thread.gmane.org/gmane.linux.ports.arm.kernel/12750][archive 2]]


Some current methods for handling the MAC address programming:
   * use custom ATAGs (ARM systems)
   * use a [[U-Boot.UBootFdtInfo][Flattened Device Tree]] (if your arch/port supports it)
   * parse the U-Boot environment directly
   * pass it via the command line

If your device driver does not support one of these sources directly, then do it yourself:
   * add an init board hook
   * program it from user space (`ifconfig hw ...`)
   * for people who need to do NFS root or similar, then use initramfs -- this is what it was designed for !
14.3.10. Mounting a Filesystem over NFS hangs forever		1. Abstract		14.3.12. Loopback interface does not work
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