Re: [PATCH 5/7] pci: Export the pci_restore_msi_state() function

On Mon, 2007-10-22 at 13:13 -0500, Linas Vepstas wrote:

On Mon, Oct 22, 2007 at 11:49:24AM +1000, Michael Ellerman wrote:

quoted

On pseries there's a chance it will work for PCI error recovery, but if
so it's just lucky that firmware has left everything configured the same
way. 

? The papr is quite clear that i is up to the OS to restore the msi
state after an eeh error.

Perhaps. I see R1-7.3.10.5.1-10, which says we should restore the config
space after a reset operation, but after an isolate/unisolate we must
recall RTAS. I thought EEH was doing the isolate/unisolate, but if it's
just a reset then just blatting the config space back should work.

quoted

Yes I think so. That way we can properly reconfigure via the firmware
interface. The other option would be to design some new arch hook to do
resume, but just doing a disable/enable seems simpler to me.

Err, If you read the code for suspend/resume, it never actually calls
disable/enable (and thus doesn't go to the firmware); it calls 
restore_msi_state() function!

I know. That was a proposed solution, to explicitly call disable/enable
instead of restore_msi_state().

If suspend/resume needs to call firmware to restore the state, then,
at the moment, suspend/resume is broken.  As I mentioned earlier,
I presumed that no powerpc laptops currently use msi-enabled devices,
as otherwise, this would have been flushed out.

On _pseries_ suspend/resume with MSI is broken. The other powerpc
platforms that implement MSI should be fine, although I don't think
anyone's tested them, because they're not laptops and so suspend/resume
is not that interesting.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person