Re: flashing milo on udb

David A Rusling (rusling@linux.reo.dec.com)
Mon, 25 Nov 1996 09:53:43 +0000


> I have hacked a version that can write the flash on a UDB. However, it is
> not yet useful, as Milo won't actually work out of flash on the UDB (yet).
> Some changes will need to be made to Milo to handle the complete cold-start
> initialization of the UDB correctly.
>

We discovered some differences in the serial port init between noname and UDB.
As UDB was loaded by ARC, I let ARC set those up and then made sure that the
code doesn't unset things. Apart from that I don't recall any differences.

> This will probably result in the need for separate UDB and Noname
> configurations for Milo, unless someone can recommend a good way to detect the
> difference at runtime.

That _may_ be your only way although you can detect that you booted either via
WNT or someother way.

> `I've though about using the presence of the Intel
> 82365 (?) ISA to PCMCIA interface, or the Microsoft Sound System, however both
> of these could be plugged into an ISA slot on a Noname. I thought about trying
> to detect whether the SROM code is from the UDB or the Noname, but as far as
> I know the SROM code is *only* loaded into the Icache, so there is no way to
> inspect it as data. Maybe I could look at the return address on the stack
> when the SROM calls the loaded flash image; it might be different. Then again,
> the SROM may just _jump_ to the image rather than calling it. I don't
> actually have a Noname, so it will be difficult for me to develop autodetection
> code of any sort.
>
> Also, I need to add an option for Milo to allow setting the boot option on
> the UDB, so that it will be possible to switch back to ARC or SRM. Note that
> there is not room in the flash for ARC, SRM, and Milo, so you'll have to give
> up one of them.
>

That command already exists, look in milo.c, it's called 'bootopt' and only gets
built in for systems that support it, ie EB164, PC164 etc and these use a byte in
the TOY clock to store the bootopt. The SROM code can then easily read it.

> Anyhow, if I get Milo working from flash on the UDB (and I'm not promising
> that I will have time to do it), I'll contribute the changes back to
> Dave Rusling to merge into the standard Milo distribution.
>

Good, I'll be happy to accept them.

Dave
----------------------------------------------------------------------
David A Rusling Principal Engineer
European Semiconductor Applications Digital Equipment Co Ltd.,
Engineering PO Box 121,
Imperial Way,
Worton Grange
Reading RG2 0TU
Linux, Alpha, StrongArm, PCI Tel: UK-(0)1734-204380
Fax: UK-(0)1734-203133
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