Random comments on LinuxBIOS
steve at nexpath.com
Thu Apr 17 11:43:01 CEST 2003
Eric W. Biederman wrote:
>>I also think we should default to
>>wp cacheing for the flash region as well.
> WP caching?? We should cache it certainly but note
> that WP caching != Write Protect in the normal sense.
> Except for the location the 16->32bit transition this is pretty much
> what the code currently does. And for our ``normal'' images when
> we have 2 copies of LinuxBIOS the start up is entirely 32bit.
I was referring to memory type=5, which Intel calls WP (vol 3, 10-23).
It is not by default done for the upper 4G regions in linuxbios AFAIK
(biosbase=0xffff0000). One has to set XIP_ROM_BASE, XIP_ROM_SIZE, and
then an mtrr is set of type 5 for this region, I am pretty sure. It
made a big difference in the pcchips787, as I could not use compression
otherwise, took too long to decompress, and the watchdog reset kicked
off. I have not studied in detail what WP means precisely but I know
that others use this type for flash regions.
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