linux-kernel - Re: PCI PM: Restore standard config registers of all devices early

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Date:	Tue, 03 Feb 2009 12:46:46 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Andreas Schwab <schwab@...e.de>, Len Brown <lenb@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: PCI PM: Restore standard config registers of all devices early


> Note how the PCI layer (currently) only saves the low _16_ dwords of 
> config space (64 bytes). The radeonfb code that did it by hand saved the 
> whole 64 dwords (256 bytes). It _probably_ doesn't matter, but..
> 
> The reason the PCI layer only does 64 bytes is that that was the really 
> old PCI config space model - the rest was undefined and apparently a few 
> cards reportedly even crashed when accessing it (but who knows, that may 
> be urban folklore).
> 
> But if that patch works for you, it's clearly already better than _not_ 
> applying the patch, so..

Radeons don't do much with config space... the worst we may miss I
suppose is subsystem vendor/device... Maybe I'll add something to
explicitely save and restore it or X might get upset. I'll have a look.

At some point, that whole code will migrate out of radeonfb into the new
radeon DRM with kernel mode setting in which case even X should stop
caring ... mostly.

Cheers,
Ben.


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