[Cerowrt-devel] [Babel-users] Why we are discussing ARM [was: Cross-compiling to armhf]

[Jonathan Morton]

> On 26 Jun, 2016, at 22:02, Baptiste Jonglez <baptiste at bitsofnetworks.org> wrote:
> 
>> Do you know how the Ethernet is hooked to the SoC?  I could be wrong, but
>> I don't think Allwinner SoCs include GMII.
> 
> I suggest you look at the schematics (here for LIME2):
> 
>  https://github.com/OLIMEX/OLINUXINO/raw/master/HARDWARE/A20-OLinuXino-LIME2/A20-OLinuXino-Lime2_Rev_G.pdf
> 
> Looking quickly, this looks like a SPI interface.  I'm really not a
> hardware expert though, so you'd better check yourself.

It looks like GMII to me.  That’s a good thing.

SPI would be extremely unlikely - it just doesn’t have that sort of bandwidth, and I’ve never heard of it being used to attach Ethernet before.  It appears that some of the pins used for GMII on the AllWinner are shared with one of the SPI interfaces (and a serial UART) - they can be used for one purpose or the other, but not both.  This is quite common practice in the embedded world.

 - Jonathan Morton