grackle, patches, MMU, ...

Benjamin Herrenschmidt bh40 at calva.net
Fri Jan 1 09:24:53 EST 1999


On Thu, Dec 31, 1998, Cort Dougan <cort at persephone.cs.nmt.edu> wrote:


>The # of free bats depends on the machine.  We'd only have all the bats
>free if we map without the BATS entirely.  We don't to switch between
>mapping with and without BATS on the kernel depending on the process.

Ok. I knew for the variable number of BATs. So currently, the BATs are
set once
for all for the kernel, and stay this way in user mode. Getting them
beeing switched on a per-process basis would require changes still beyond
my current knowledge about the kernel. I'll try to understand all this
and I'll eventually code some test stuffs. Once BATs are switched, we can
use them for large ioremaps.

>PCI is a lot bigger than one bat.  On prep we map all the pci space we use
>with a bat.

Yep, of course, I was thinking about what is currently allocated, and
this is usually fine for one BAT.

For the curious, MacOS uses BATs too, but it can only use BATs for PCI,
no pages :-( This makes things quite funny when trying to use several
cacheable regions on a board.


-- 
           E-Mail: <mailto:bh40 at calva.net>
BenH.      Web   : <http://calvaweb.calvacom.fr/bh40/>



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