Re: [patch 2.6.12 (repost w/ corrected subject)] pci: restore BAR values in pci_enable_device_bars

Russell King
2005-07-06T07:46:19Z

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On Wed, Jul 06, 2005 at 03:34:54AM +0400, Ivan Kokshaysky wrote:
> On Tue, Jul 05, 2005 at 10:46:20PM +0100, Russell King wrote:
> > On Tue, Jul 05, 2005 at 09:05:55PM +0100, Matthew Wilcox wrote:
> > > 64-bit BARs work fine on 64-bit machines. I'm ambivalent whether we
> > > ought to support 64-bit BARs on 32-bit machines.
> >
> > This only occurs because the problematical functions (eg,
> > pci_update_resource) probably aren't called on 64-bit machines - if
> > they were, they'd zero the upper 32-bits. Maybe 64-bit machines are
> > happy with that anyway?
>
> Why problematical? It's just the way how linux has always dealt with
> 64-bit BARs - put everything below 4G in the bus address space, on *any*
> architecture. I'd be quite surprised if some firmware doesn't do the same
> thing - so far I haven't heard any complaints.

If this is so, Grant's concern about programming the top half of 64-bit
resources with zero isn't appropriate. However, he did raise this as
an issue...

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core