linux-kernel - Re: [PATCH] x86/pci: don't use crs for root if we only have one root bus

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Date:	Wed, 24 Jun 2009 16:37:05 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Gary Hade <garyhade@...ibm.com>,
	Matthew Wilcox <matthew@....cx>,
	Larry Finger <Larry.Finger@...inger.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pci@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jaswinder Singh Rajput <jaswinder@...nel.org>
Subject: Re: [PATCH] x86/pci: don't use crs for root if we only have one
 root bus

On Wed, 24 Jun 2009 16:21:09 -0700 (PDT)
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> 
> 
> On Wed, 24 Jun 2009, Linus Torvalds wrote:
> >
> > I'm happy to apply various patches to fix it up, but regardless, I
> > thinkwe should revert that commit as bogus. We can try making it
> > the default again next round, when maybe it will be true that it
> > doesn't cause issues.
> 
> Btw, I really think our _CRS handling sucks.
> 
> There's two things that you can do with _CRS:
> 
>  - use the _existence_ of it as an indicator of a root bus
> 
>  - try to use it to populate the resource tree.
> 
> And quite frankly, I think #2 is broken. There's no way in hell that
> ACPI tables are ever going to be better than just asking the
> hardware. We've gone through this before. Trusting ACPI over the
> hardware is just FUNDAMENTALLY WRONG.
> 
> So I'm just going to do that revert. I'm not sure if it ever makes
> sense to make that insane _CRS code the default. It seems like a
> fundamentally flawed idea.

Yeah, I think it's reasonable to revert, especially given how we do
_CRS handling currently.  I'm hoping at some point we can use the _CRS
data to at least augment the configuration we get from hardware, since
on some machines it seems to be necessary.

-- 
Jesse Barnes, Intel Open Source Technology Center
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