crosscompiler and porting notes

[Chuck Robey]

Mark Tinguely wrote:
> sorry for the blank reply. It should have said
> 
> Looking at the current sources for the GNU assembler, it appears to me that
> the "gas" sources do not have some new and important ARMv7 commands such as
> "dmb", "dsb", and "isb" (barriers). There ARMv6 equivalent command, but
> are not recommended.
> 			---
> I looked at the Cortex document, the first thing that changed in ARMv7
> is the information registers (for example information on the caches).
> You will need to replace the CPU information and intialization code.
> 
> It would be nice to get an ARMv7 ARM. Someone with authority, like the
> FreeBSD Foundation may be needed.
> 			---
> You will need to write a new cpufunc_asm_XXX.S file of routines. The
> existing routines assume the pmap will flush the caches on context change.
> 			---
> I would suggest you start by using the existing memory model of flushing
> caches on context changes until we learn more on the Cortex cache - are they
> *really* not effected by the cache coloring problem.
> 
> If you can get the console working, and are willing to put some test
> code into somewhere like pmap_bootstrap(), to test if the cache coloring
> is really fixed, I would write it up.
> 			---
> I have some rough code for the new ARMv6/ARMv7 TLS registers, the tlb ASID
> and load and store exclusive. You have plenty to do to get the board up
> to single user, without having to worry about this other stuff.

Thanks for the comments, Mark, I'll use them to begin my code research.  I would
VERY much like to put my hands on whatever is written today, and I actually do
hope that it's not all written today, I would like to add to the code, it's a
learning experience.  I also have probably a fiar amount of time, because I sent
away for the Pandora about 6 weeks ago, and it looks like it won't ship for
maybe another month or two.  I'm really anxious for it to show up, but it does
allow me to start the research right away.

> 
> --Mark.