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SubjectRe: [PATCH] HPET driver
On Thu, May 13, 2004 at 07:49:22PM -0400, Jeff Garzik wrote:
> Andrew Morton wrote:
> >Jeff Garzik <jgarzik@pobox.com> wrote:
> >
> >>>+ vma->vm_flags |= (VM_IO | VM_SHM | VM_LOCKED);
> >>>+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> >>>+ addr = __pa(addr);
> >>
> >>where did these flags come from? don't you just want VM_RESERVED?
> >
> >
> >VM_IO is the way to mark mmapped I/O devices.
> >
> > vma->vm_flags |= VM_IO;
> >
> >should be sufficient here.
> >
> >hm, I'm trying to decrypt how the driver accesses the hardware. It's
> >taking copies of kernel virtual addresses based off hpet_virt_address, but
> >there are no readl's or writel's in there. Is the actual device access
> >done over in time_hpet.c?
>
>
> HPET writes into RAM at magic addresses, so it's not really a bus address.

Since it lives in the bridge (either north or south), IMO it is a bus
address ... at least on AMD machines it's the same space where MMIO
comes from.

> Thus I think only VM_RESERVED is needed...
>
> Jeff

--
Vojtech Pavlik
SuSE Labs, SuSE CR
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