Most I/O in the kernel is done using the kernel offset mapping.
However, there is one API that uses aliased kernel address ranges:

> The final category of APIs is for I/O to deliberately aliased address
> ranges inside the kernel.  Such aliases are set up by use of the
> vmap/vmalloc API.  Since kernel I/O goes via physical pages, the I/O
> subsystem assumes that the user mapping and kernel offset mapping are
> the only aliases.  This isn't true for vmap aliases, so anything in
> the kernel trying to do I/O to vmap areas must manually manage
> coherency.  It must do this by flushing the vmap range before doing
> I/O and invalidating it after the I/O returns.

For this reason, we should use the hardware lpa instruction to load the
physical address of kernel virtual addresses in the driver code.

I believe we only use the vmap/vmalloc API with old PA 1.x processors
which don't have a sba, so we don't hit this problem.

Tested on c3750, c8000 and rp3440.
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>