RE: [PATCH] reverse pci config space restore order

[abelay@MIT.EDU]

Quoting "Brown, Len" <len.brown@intel.com>:

>
>> On Tue, 2006-04-25 at 11:48 +0100, Matthew Garrett wrote:
>>> On Tue, Apr 25, 2006 at 02:50:57PM +0800, Yu, Luming wrote:
>>>
>>> > -	for (i = 0; i < 16; i++)
>>> > +	for (i = 15; i >= 0 ; i--)
>>>
>>> We certainly need to do /something/ here, but I'm not sure
>>> this is it.
>>> Adam Belay has code to limit PCI state restoration to the
>>> PCI-specified
>>> registers, with the idea being that individual drivers fix things up
>>> properly. While this has the obvious drawback that almost every PCI
>>> driver in the tree would then need fixing up, it's also probably the
>>> right thing.
>>
>> it has a second drawback: it assumes all devices HAVE a driver, which
>> isn't normally the case...
>
> Adam mentioned earlier, and I agree, that it is probably a bad
> idea for this code to blindly scribble on the BIST field at i=3.
> Probably we should clear that field before restoring it.
>
> Re: this patch
> I think that this patch is likely a positive forward step.
> It seems logical to restore the BARs before the CMD/STATUS in general,
> nothing specific to the ICH here.
>
> But yes, this is a helper routine and devices where it hurts
> instead of helps should have their own routine.  Complex devices
> need to handle the device-specific config space state above these
> 1st 16 locations anyway.

Right, and because we only restore the first 0x40 or so registers (they're all
standard), I don't think implementing pci_save/restore_state() properly 
is going
to break much at all.  I'm planning to merge these changes with -mm, so
hopefully it won't be difficult to tell. :)

Re: devices without drivers

We can certainly call a generic save and restore function when there isn't a
driver available, but beyond handling standard registers mentioned in 
the spec,
if important hardware context is lost there's really no way around it.

-Adam