mmap question on ppc440
benh at kernel.crashing.org
Wed Nov 7 09:02:10 EST 2007
On Tue, 2007-11-06 at 07:50 +0100, Stefan Roese wrote:
> On Monday 05 November 2007, Josh Boyer wrote:
> > > I am attempting to access the CPLD on the AMCC Sequoia board from
> > > user-land. I open /dev/mem, and mmap it, then try to access the
> > > resulting pointer. That works fine when accessing physical addresses
> > > that correspond to RAM, but as soon as I try to access the CPLD at
> > > physical address 0xc0000000, I get an infinite machine check.
> > That's because the CPLD is actually at physical address 0x1C0000000.
> > Yay for 36-bit physical addresses.
> Right. Are you using arch/ppc or arch/powerpc? If it's arch/ppc you could
> give the following patch a try:
> @@ -275,6 +275,14 @@
> size_t size = vma->vm_end - vma->vm_start;
> +#if defined(CONFIG_44x) && !defined(CONFIG_PPC_MERGE)
> + /*
> + * 2006-08-07: sr
> + * Needed on 44x-er systems for 36bit addresses (like pci on 440gx)
> + */
> + vma->vm_pgoff = (fixup_bigphys_addr(vma->vm_pgoff << PAGE_SHIFT, size) >> PAGE_SHIFT);
> if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
> return -EINVAL;
I think we need to ditch the bigphys fixup stuff and come up with a way
to make /dev/mem work with the actual 36 bits offsets (after all, it's
all pgoff, it should work).
The other problem is X of course... 32 bits X server currently cannot
cope with physical addresses > 32 bits at all. They will just blow up or
randomly scribble over /dev/mem.
The solution is libpciaccess and the new pci-rework branch of X which
uses it, but I haven't had a chance to test that properly yet on 4xx.
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