linux-kernel - Re: [patch] pci: revert "PCI: remove transparent bridge sizing"

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Message-ID: <20080326203012.GB6249@us.ibm.com>
Date:	Wed, 26 Mar 2008 13:30:12 -0700
From:	Gary Hade <garyhade@...ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Gary Hade <garyhade@...ibm.com>, Ingo Molnar <mingo@...e.hu>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Thomas Meyer <thomas@...3r.de>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	pm@...ian.org
Subject: Re: [patch] pci: revert "PCI: remove transparent bridge sizing"

On Wed, Mar 26, 2008 at 11:33:24AM -0700, Linus Torvalds wrote:
> 
> 
> On Wed, 26 Mar 2008, Gary Hade wrote:
> >
> > I have a fix for the ThinkPad docking Oops but if the issue being
> > discussed here is caused by the transparent bridge sizing removal
> > change I totally agree that it should be reverted.  
> 
> Ok, I reverted it, but the docking Oops is still interesting, in that it 
> implies that some piece of code wasn't exactly robust. I haven't seen the 
> patch, but it sounds like that should be fixed independently..

Could be but without the sizing removal I doubt that the fix I
was going to propose (see below) would be the same.  What I had
found is that the removal of the transparent bridge sizing was
leaving the resource record for at least region 7 (IO) of a
hot-added transparent bridge on the docking station in a state
that was not palatable with later executed code in pdev_sort_resource().
Even though the restoration of the transparent bridge sizing
corrects the problem, pdev_sort_resource() could probably use
some bulletproofing.  I will take a look at this.

Thanks,
Gary

-- 
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503  IBM T/L: 775-4503
garyhade@...ibm.com
http://www.ibm.com/linux/ltc


--- linux-2.6.25-rc6/drivers/pci/probe.c.orig	2008-03-20 12:09:14.000000000 -0700
+++ linux-2.6.25-rc6/drivers/pci/probe.c	2008-03-20 12:11:29.000000000 -0700
@@ -328,6 +328,8 @@ void __devinit pci_read_bridge_bases(str
 		if (!res->end)
 			res->end = limit + 0xfff;
 	}
+	if (!res->start && dev->transparent)
+		res->flags = 0;
 
 	res = child->resource[1];
 	pci_read_config_word(dev, PCI_MEMORY_BASE, &mem_base_lo);
@@ -339,6 +341,8 @@ void __devinit pci_read_bridge_bases(str
 		res->start = base;
 		res->end = limit + 0xfffff;
 	}
+	if (!res->start && dev->transparent)
+		res->flags = 0;
 
 	res = child->resource[2];
 	pci_read_config_word(dev, PCI_PREF_MEMORY_BASE, &mem_base_lo);
@@ -373,6 +377,8 @@ void __devinit pci_read_bridge_bases(str
 		res->start = base;
 		res->end = limit + 0xfffff;
 	}
+	if (!res->start && dev->transparent)
+		res->flags = 0;
 }
 
 static struct pci_bus * pci_alloc_bus(void)
--
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