[Openec] fail-safe startup code?

[Richard A. Smith]

Frieder Ferlemann wrote:

> And the data sheet mentions the existence of
> "XBI registers A0-A3h(bank select)" in the descripion for
> Bit 4 in XBICS so presumably for some versions of silicon
> these registers might be there.
> 
> If XBISEG2 and XBISEG3 are implemented then we'd need a
> hefty extra portion of flash but using a fancy memory map
> like:
> 
> 0x000000-0x003fff  for the fail-safe routine
> 0x004000-0x00ffff  unused (or used for stuff never expected to be changed)
> 
> 0x010000-0x01ffff  for normal openec code (visible at 0x0000-0xffff
>                    to the 8051 after the fail-safe routine decides to
>                    remap it there)
> 
> the fail-safe code could then survive even if 0x010000-0x01ffff
> is spoiled (due to buggy openec code OR due to power failure during
> the flashing itself).

Dude! If you can make that work you will be a big OLPC hero.  None of us 
knew that this possibility existed.  Thats huge.

Bad flashing in the field is a _big_ concern for us because it turns the 
laptop into a brick and the service cost is more than the cost of the 
laptop itself.

I know you aren't  big on your work efforts going back into close source 
trees but this is absolutely a feature that I would add into the current 
code base.

/me goes to read up on XBISEG2 and 3.

-- 
Richard Smith  <richard at laptop.org>
One Laptop Per Child