[U-Boot] [PATCH] net: write enetaddr down to hardware on env_callback

[Bin Meng]

Hi Hannes,

On Tue, Sep 6, 2016 at 3:23 PM, Hannes Schmelzer
<Hannes.Schmelzer at br-automation.com> wrote:
> Bin Meng <bmeng.cn at gmail.com> schrieb am 06.09.2016 09:07:39:
>
> [...]
>> >>
>> >> Why is this needed? The MAC address is supposed to be programmed in
>> >> the driver's probe routine.
>> >
>> > For example on my custom ZYNQ board.
>> > The Ethernetcontroller within the ZYNQ has no ROM to store his own
>> > MAC-Address, further no MAC is stored within environment.
>> > So Ethernet gets probed with a "random MAC-Address" if configured.
>> >
>> > Later somebody (like me) oder something (my bootscript) runs "setenv
>> > ethaddr ...." on the console.
>> > Result is (was before this patch), that all networking infrastructre
> is
>> > running this new mac, but hardware is running the old (random) one and
>> > networking is simple not functional.
>> >
>>
>> This indicates that your ethernet driver does not program the latest
>> MAC address everyone when it gets probed. The driver should be fixed.
>
> The driver doesn't get probed again if mac-address is changed using
> "setenv ethaddr",
> so it has no chance to program anything.
>

Yes, driver is not probed when "setenv ethaddr", but next time when
you type any ethernet related command (like tftpboot), the driver will
be probed.

> For program i understand, in this case with zynq, overtaking mac-address
> into his registers.
> There is per default no ROM to store some mac.
>

I have feeling that for some ethernet controllers, simply calling
eth_write_hwaddr() may not change its MAC address correctly. It may
need some special programming sequence like firstly turn off, reset,
then program the MAC.

Regards,
Bin