[coreboot] [PATCH] xcshell: serial shell for early debugging

[Carl-Daniel Hailfinger]

On 14.07.2009 18:55, Michael Gold wrote:
> On Tue, Jul 14, 2009 at 08:38:15 -0700, ron minnich wrote:
>   
>> I like it. We talked about something like this in v3. How would you
>> feel about putting in emergency flash upgrade support :-)
>>     
>
> I like the flash upgrade idea, but I'm not sure how to do it yet (in a
> generic way).  Any suggestions?
>   

If you have RAM, downloading a flashrom binary linked against libpayload
would be best. The good news is that flashrom itself is written in a way
that allows you to put it on top of any backend, even a backend which
does nothing but perform remote control of xcshell. I think that would
be easiest.

> I think it might be possible without any changes by marking the part of
> the ROM containing xcshell as cacheable, and then using pokes to rewrite
> the rest of the chip.  It would be slow, but a small flash upgrade
> program could be uploaded that would do the rest of the work more
> quickly.
>   

If you have a generic "write X to loation y" interface, flashrom can
deal with that, even remotely.

> My original idea was that one would set up CAR, upload code, and jump to
> it; this would allow the system to be extended without having to include
> much code.  It doesn't work, at least on my Pentium 3, but the same
> thing could be done with RAM once it's initialised (or with flash for
> occasional use).
>   

As long as RAM works, we could even upload a complete flashrom binary
over zmodem.

Regards,
Carl-Daniel

-- 
http://www.hailfinger.org/