Re: CVS commit: src/sys/arch/powerpc

[Simon Burge <simonb%NetBSD.org@localhost>]

"Masao Uebayashi" wrote:

> Module Name:  src
> Committed By: uebayasi
> Date:         Sat Nov  6 16:36:27 UTC 2010
> 
> Modified Files:
> 
>       src/sys/arch/powerpc/ibm4xx: pmap.c
>       src/sys/arch/powerpc/include/ibm4xx: vmparam.h
> 
> Log Message:
> 
> Merge from uebayasi-xip:
> ----------------------------
> revision 1.60.2.5
> date: 2010/08/14 02:09:57;  author: uebayasi;  state: Exp;  lines: +2 -1
> Teach TLB miss handler (pmap_tlbmiss()) to map "Expansion ROM" area as
> PA == VA.  Now we don't need to reserve a TLB entry for it.
> ----------------------------

At a quick glance, this seems to hard-wire in device addresses which may
not be the same on every ibm4xx platform (the 0xef000000 address).

Also I'm not sure I like the idea of modifying a general pmap to have
knowledge of device-specific "Expansion ROM" address ranges.  Are these
_always_ guaranteed to live in the address range you've specified or
is there a chance a ROM could be mapped at different addresses on some
boards?  The change as is also limits expansion ROMs to a bit over
256MB which mightn't be a problem now but also indicates a problem with
hardcoding specific values in a general pmap.

I'm not sure what the "correct" way of doing this is.  I think I'd
prefer to see some sort of registration of expansion ROM space that you
want to reserve, but would need to put some more thought in to it.

If this change was to remain in its current form, the comment
immediately above the change you made in the tlb miss handler is now
incorrect and would need to be adjusted.

Cheers,
Simon.