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Re: CC112 VME board

On Sun, 2003-06-01 at 15:58, Frank Gevaerts wrote:
> I have a compcontrol cc112 VME board. Specs are:
> - 20 MHz 68030/68882

Should be no problem.

> - 4 MB local RAM

Hmm. That's not much RAM. But if you don't need networking it might work
(painfully slow though). Do you have VME RAM? Or a VME Ethernet board?

> - 2 serial ports (SCN2681)

I am writing a driver for this chip at the moment. I already have a
basic one based on drivers/char/sb1250_duart.c (which looks a lot like
the SCN2681) but I'm now writing one using the generic_serial framework.

Early startup and serial console works fine. In the current version of
arch/m68k/kernel/head.S there is already support for the SCN2681 since
this chip is also present in the Apollo port.

> - SCSI (wd33c93)

Probably shouldn't be a problem if you get the DMA working.

> - an OS/9 boot eeprom with debugger

If you can download code this greatly simplifies things ;-)

It also helps if there are entry points into the firmware so you can use
it to do boring stuff like read from the harddisk or write to the serial
port. I recently ported Linux/m68k to a Plessey CPU board which has just
about NO firmware, which wasn't too much fun.

> I have full documentation, but not enough time/experience to get linux
> running on this. I have so far managed to load some code from a serial
> port that printed some messages to the other serial port, but I'm lost
> as soon as I look at the kernel boot and memory mapping code.

Well, most of the memory mapping code is generic these days. All you
basically need to do is add some mappings for the I/O regions if they're
mapped in low memory normally, moving them up. Or, if they are already
'up there' you can just use transparent translation. All this can be
done using some simple macros, plenty examples in the file.

You might also want to add support for printing some characters on one
of your serial ports there. Shouldn't be too hard.

I only had to add about 40 lines of code to head.S for the Plessey port.

Getting a boot loader working is IMO a lot harder than getting the basic
kernel to work. It took me about 2 weeks to add a new port to VMELILO
and only 2 days or so to get my first kernel panic ;-) 

If you have callable firmware it makes things a lot easier. I had to
write a small SCSI driver...

> I guess that once I have a booting kernel I can manage the individual drivers.
> I would like to get this running so I can use my VME serial and digital
> IO boards, but I do not really know how to proceed. Another alternative
> would be trading it for a supported VME board with someone who likes a
> challenge.

If you need more help, please contact me directly. I'd be happy to help
you out.

Kind regards,


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