Re: pgprot_writecombine & shub 1.x

David Mosberger
2005-01-19T17:53:38Z

>>>>> On Wed, 19 Jan 2005 09:28:27 -0800, Jesse Barnes <jbarnes@sgi.com> said:

Jesse> On Wednesday, January 12, 2005 10:51 am, Jim Hull wrote:
>> I'm not really qualified to design the right linux interfaces,
>> but to be IPF compliant, you need to change all such places to
>> first consult the EFI memory map. Whether you do this once at
>> boot time, on every call, whether to fail an unsupported request
>> or remap the attribute to something the platform can support
>> (e.g., mapping WC to UC), is all up to you.

Jesse> So I guess we need to add ia64_set_page_wc() and
Jesse> ia64_set_page_uc() functions that set the appropriate page
Jesse> bits or return errors if the EFI memory map says a particular
Jesse> mode isn't allowed? How does that sound to you, Tony &
Jesse> David? Fortunately there aren't that many users of
Jesse> pgprot_writecombine so fixing them up should be easy.

I'm still not clear which case you're concerned about: mapping I/O
memory with WC or mapping real memory with WC. For the latter, I
think we may need an API to allocate memory that can be mapped WC (if
possible at all).

--david