[RFC] m68k: network interface on amcore board

[RFC] m68k: network interface on amcore board

[Angelo Dureghello]

Hi all,

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 ?

Thanks,

Best regards,
Angelo Dureghello

Re: [RFC] m68k: network interface on amcore board

[Geert Uytterhoeven]

Hi Angelo,

On Mon, Oct 31, 2016 at 8:26 AM, Angelo Dureghello <angelo@sysam.it> 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!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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

Re: [RFC] m68k: network interface on amcore board

[Angelo Dureghello]

Hi Geert,

On 31/10/2016 09:01, Geert Uytterhoeven wrote:
> Hi Angelo,
>
> On Mon, Oct 31, 2016 at 8:26 AM, Angelo Dureghello <angelo@sysam.it> 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.

Best regards,
Angelo Dureghello



> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> 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
>

Re: [RFC] m68k: network interface on amcore board

[Greg Ungerer]

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 <angelo@sysam.it> 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 -- geert@linux-m68k.org
>>
>> 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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