Delay in copying Linuxbios to ram

[Eric W. Biederman]

SONE Takeshi <ts1 at tsn.or.jp> writes:

> On Fri, Apr 25, 2003 at 06:55:37PM -0600, Eric W. Biederman wrote:
> > > > In cpu/p6/earlymtrr.inc, 0xf0000-0xfffff is left uncached.
> > > > (Only 0-640KB is cached, 640KB-1M is uncached)
> > > > I will try adding code there to set fixed MTRR for 0xf0000-0xfffff
> > > > WP caching.
> > > > It should be harmless for other boards that do not need this,
> > > > what do you think?
> > > >
> > > 
> > > Not sure.  Need to see if the RAM is turned on for this region later after
> the
> 
> > > C-code starts, if so, then the cache memory type may have to be changed from
> WP
> 
> > > to normal.
> 
> I tried it anyway and it worked great.
> Now I can't see anything between 'Copying LinuxBIOS to ram' and
> IDE loading message because it's too fast! 
> 
> > The generic code should handle this.  I believe all of the mtrrs are rebuilt.
> 
> I think it's rebuilt in mtrr.c.
> 
> My modification is below.

``Write Protect'' in the mtrrs does not mean write protected.  It is a strange
messed up form of write-through.  In particular it dumps the cache on writes
it does not forbid writes.

Unless you know of a situation where write protect is more appropriate please
use write-through.  It is less confusing, and since no one is writing to that
area anyway it gives the exact same result, reads are cached.

Eric