Re: Specifying properly the PCI driver model on all linux archite ctur es, (ioremap(), bus_to_virt()

Jakub Jelinek (jakub@redhat.com)
Tue, 2 Nov 1999 17:48:25 +0100

> Where in the heck did you find that?
>
> I was under the impression that the readb/w/l and writeb/w/l were only for
> spaces marked as I/O space in PCI. I thought that if it was in PCI memory
> space you could directly reference the address after you used ioremap().
>
> If this is true, you can't just directly access the virtual address, then
> somebody should really add this information to the Documentation/pci.txt
> file.

The address returned by ioremap is not a virtual address, it is a cookie
which readb/w/l etc. take as arguments.
E.g. on sparc64, ioremap returns you the physical address (ie. ioremap just
returns first argument and does nothing else) and readb and the like use
instructions to bypass caches which take that physical address (so that it
does not use any TLB entries).

Cheers,
Jakub
___________________________________________________________________
Jakub Jelinek | jakub@redhat.com | http://sunsite.mff.cuni.cz/~jj
Linux version 2.3.18 on a sparc64 machine (1343.49 BogoMips)
___________________________________________________________________

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