Re: [PATCH] x86/pci: do assign root bus res if _CRS is used
From: Jesse Barnes
Date: Tue Jun 16 2009 - 17:54:56 EST
On Wed, 27 May 2009 12:41:44 -0700
Gary Hade <garyhade@xxxxxxxxxx> wrote:
> On Thu, May 21, 2009 at 09:37:37AM -0700, Gary Hade wrote:
> > On Thu, May 21, 2009 at 08:46:17AM -0600, Bjorn Helgaas wrote:
> > > On Wednesday 20 May 2009 5:49:10 pm Jesse Barnes wrote:
> > > > On Fri, 8 May 2009 16:40:10 -0600
> > > > Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote:
> > > > > Did anything happen with this?
> > > > >
> > > > > The longer we wait to make "use_crs" the default, the harder
> > > > > it will be, so I'd like to push ahead.
> > > >
> > > > Here's a patch to make CRS the default. If it looks ok I can
> > > > push it into my linux-next branch. I'm all for using reliable
> > > > data from the BIOS. I guess we'll find out fairly quickly if
> > > > this stuff isn't...
> > >
> > > Thanks for following up on this, Jesse. It was on my to-do list
> > > for yesterday, but I didn't get to it.
> > >
> > > Yinghai mentioned a specific box where we might have trouble, but
> > > we never got enough details to really debug it. So I think we
> > > might as well give it a shot and fine-tune it as we need to.
> > I just remembered that Andrew Morton once raised some concerns
> > related to the number of _CRS returned resources exceeding the
> > fixed resource array size -> http://lkml.org/lkml/2007/11/1/49
> > I believe PCI_BUS_NUM_RESOURCES was later increased but if
> > that increase was insufficient to cover all systems that the
> > code will now be exposed to, it seems like the "And should we
> > really be silently ignoring this problem? Should we at least
> > report it?" comment that was not addressed could become relevent.
> Not only do we not warn, if we did warn based on the current
> 'if (info->res_num >= PCI_BUS_NUM_RESOURCES)'
> resource array overrun avoidance criteria it would be incorrect
> for a root bus that is connected to a subordinate bus with a
> transparent bridge. We need to avoid the last 3 slots of the
> resource array since they do not get mapped to a transparent
> bridge connected subordinate bus. I believe the below patch
> addresses these issues.
> With PCI_BUS_NUM_RESOURCES currently at 16 we still have space
> to accomodate 13 _CRS returned resource descriptors which will
> hopefully be sufficient.
Ok, just applied this one to my linux-next tree, since we'll want it
now that _CRS is used by default.
Len, is this ok with you? It touches x86 ACPI files rather than PCI
files, but it's pretty tightly related...
Jesse Barnes, Intel Open Source Technology Center
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