what happens if we run out of bats?
Then it returns NULL and the caller must handle it. The board port
maintainer needs understand the board/CPU/SoC and not depend on more
BATs than are available. They also need to understand that there is a
tradeoff between BATs for IO and BATs for RAM. If the board port uses
up all the BATs for IO, then RAM above 256MB ends up getting mapped
with PTEs and there is a performance hit. My expectation is that only
platform code will use this facility. Device drivers should continue
to use ioremap() and will gain the benefit of the BATs if platform
code already set them up. I can add some text to the documentation to
describe this.
I'm not going to make any attempt to fallback to PTEs for IO when
there isn't enough BATs. Doing so adds an order of magnitude more
complexity.
that's fine.. I just didn't look at setbat() to see it errors out.
Also can we get rid of LOAD_BAT in head_32.S?
- k
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
