[openfirmware] On Raspberry Pi

[James Cameron]

On Mon, Jan 05, 2015 at 08:34:45AM +0000, Mark Morgan Lloyd wrote:
> James Cameron wrote:
> >For interest, a port of a Forth to Raspberry Pi happened in the last
> >couple of months.  There's enough working code there to make a port of
> >Open Firmware slightly less effort.
> >
> >https://github.com/organix/pijFORTHos
> 
> I think the problem here is that for OpenFirmware to really be
> useful, i.e. to the same extent that it is on Sun systems, it needs
> to take control as early as possible and in particular shouldn't be
> loaded from a filesystem which can be screwed. On a Raspberry Pi,
> that raises two issues:
> 
> i)  The (originally undocumented) Broadcom SoC contains firmware or
> equivalent hardware to pull a first-stage loader off the SD card. So
> the SD card is always needed, even though the mechanical connector
> is known to be one of the less-reliable components and the card
> itself will, ultimately, have a limited life.
> 
> ii) If one grits ones teeth and subverts that mechanism, one ends up
> in control of the SoC rather than in control of the application
> processer that normally runs Linux.
> 
> If one instead tolerates the existing multi-stage loader, then one
> should be able to boot Forth onto the application processor in lieu
> of Linux. But this breaks the Sun model of "Open Boot in ROM,
> everything else on disc", and loses the desirable characteristic
> that any media or controller problem returns you to the "ok" prompt
> with diagnostic capabilities, and as such I'm not sure it's worth
> the effort.

I agree.

> I'd be interested to know of any low-cost boards which could have
> OpenFirmware grafted in sufficiently early. A colleague is trying to
> build some router systems which, as a prerequisite, must have a
> serial console port.

I'm interested too.  Perhaps the BeagleBone Black?

I've brought up C Forth on the Teensy 3.1, which while it isn't Open
Firmware does share some behaviours enough to make me feel at home.
But no filesystems or TCP/IP.

http://quozl.linux.org.au/cforth-on-teensy/

-- 
James Cameron
http://quozl.linux.org.au/