[U-Boot] commit "powerpc: Remove warm reset entry point" does not work on mpc83xx

[Joakim Tjernlund]

Wolfgang Denk <wd at denx.de> wrote on 2010/10/19 22:04:17:
> 
> Dear Joakim Tjernlund,
> 
> In message <OFBC383CCF.86B567D6-ONC12577C1.006A80D5-C12577C1.
> 006AA773 at transmode.se> you wrote:
> >
> > > During normal use I thought that the reset entry point was always
> > > 0xXXXXX100 and a warm reset would never occur.
> > 
> > I am not so sure about this. Perhaps the Freescale guys can set us 
> > straight?
> 
> Originally U-Boot (well, PPCBoot, to be more precise) had this notion
> of a "warm start", but I quickly learned that this makes little sense
> in a boot loader. When we execute the "reset" command,. we usually
> want to _really_ reset the system into operational mode, including
> not only the CPU itself but also co-processors (which might be running
> some form of microcode or DMA), external controllers (to stop them
> from doing DMA or other data transfers), NOR flash (to make sure it is
> in read mode so we can execute code from it), etc.
> 
> Whenever this was not possible (usually due to hardware design
> "features") this almost always was experienced as a "bug in U-Boot"
> because there were situations where the board could only be reset
> through full power cycle.
> 
> My recommendation is: stop thinking of "warm boot"; either perform a
> "reset" (and that be a real, hard reset of the CPU core and all
> peripherals), or just continue to run ;-)

We do. Even have a HRESET button and it still doesn't work.
There is one thing though: At address 0x100(and 0x110) we have a
branch to where the boot is really located. This is because
we have small sectors in the beginning of the flash and we want to
use those as environment etc.

 Jocke