linux-kernel - Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

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Date:	Fri, 28 Dec 2007 17:06:50 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Loic Prylli <loic@...i.com>, Robert Hancock <hancockr@...w.ca>,
	Jeff Garzik <jeff@...zik.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	gregkh@...e.de, linux-pci <linux-pci@...ey.karlin.mff.cuni.cz>,
	Martin Mares <mj@....cz>, Matthew Wilcox <matthew@....cx>,
	Kai Ruhnau <kai@...getaschen.dyndns.org>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver
	opt-in


On Thu, 2007-12-27 at 21:37 -0800, Linus Torvalds wrote:
> 
> On Fri, 28 Dec 2007, Benjamin Herrenschmidt wrote:
> > 
> > I have embedded boards where proper CRS operations is critical since the
> > kernel brings the PCIe link up itself, and thus is likely to hit devices
> > still in the middle of CRS.
> 
> .. but that's perfectly fine. A PCI-E bridge will certainly retry it in 
> hardware (or it isn't a PCI-E bridge!).

Only a handful of times in many bridges I've seen.
 
> So I'm going to disable that thing. If there is some _other_ PCI-E bridge 
> that is simply buggy, and cannot handle the hw retry itself or is just 
> otherwise dodgy, we can have a white-list for cases where it really needs 
> to be done, but the current code is just bogus.

If you disable it, then isn't there also a problem with PCIE->PCI-X
bridge which will stop issuing CRS when they should ? (not sure here, I
may be a bit confused).

Ben.


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