Hi Angelo,
On 31/10/16 20:35, Angelo Dureghello wrote:
> Hi Geert,
>
> On 31/10/2016 09:01, Geert Uytterhoeven wrote:
>> Hi Angelo,
>>
>> On Mon, Oct 31, 2016 at 8:26 AM, Angelo Dureghello <[email protected]> wrote:
>>> i have still a last issue open on mcf5307-based "amcore"
>>> board i would like to fix, and need a suggestion:
>>>
>>> at design time, i wired the 32bit parallel data bus from cpu to
>>> the ethernet chip as "straight" (D0 to D0, ... D32 to D32).
>>>
>>> dm9000 driver btw works for little-endian cpu only. To have it
>>> working, i actually keep a byte "swap" patch in the driver.
>>>
>>> Since i guess i cannot pretend any driver patch for this case,
>>> i am planning a new pcb version with 32bit data bus bytes swapped
>>> in hardware.
>>>
>>> What do you think ?
>>
>> BenH has written some excellent background information about this:
>> Big and Little Endian inside / out
>> https://www.linuxplumbersconf.org/2012/wp-content/uploads/2012/09/2012-lpc-ref-big-little-endian-herrenschmidt.odp
>> https://www.youtube.com/watch?v=oBSuXP-1Tc0
>>
>> Happy reading!
>>
>
>
> many thanks for the very interesting presentation,
> so from what i understand, the issue is in this terms:
>
> * dm9000 registers/memory byte order is little endian.
> * coldfire memory byte order is big endian
>
> The proper way to fix this should be as said in the presentation
> above to swap bytes in hardware.
Does the dm9000 have to use a 16bit bus, or can you wire it
up 8bit only? Can be another option to avoid problems.
Regards
Greg
>> Gr{oetje,eeting}s,
>>
>> Geert
>>
>> --
>> Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
>> [email protected]
>>
>> In personal conversations with technical people, I call myself a hacker. But
>> when I'm talking to journalists I just say "programmer" or something like
>> that.
>> -- Linus Torvalds
>>
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