linux-kernel - Re: [PATCH] PCI: boot parameter to avoid expansion ROM memory allocation

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Message-ID: <20080513210054.GB28815@us.ibm.com>
Date:	Tue, 13 May 2008 14:00:54 -0700
From:	Gary Hade <garyhade@...ibm.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Gary Hade <garyhade@...ibm.com>, jbarnes@...tuousgeek.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI: boot parameter to avoid expansion ROM memory allocation

On Tue, May 13, 2008 at 10:48:03AM -0700, Yinghai Lu wrote:
> On Mon, May 12, 2008 at 3:30 PM, Gary Hade <garyhade@...ibm.com> wrote:
> > On Mon, May 12, 2008 at 02:43:44PM -0700, Yinghai Lu wrote:
> >  > On Mon, May 12, 2008 at 1:57 PM, Gary Hade <garyhade@...ibm.com> wrote:
> >         <snip>
> >
> > > >  --- linux-2.6.26-rc2/arch/x86/pci/common.c.orig 2008-05-12 10:59:58.000000000 -0700
> >  > >  +++ linux-2.6.26-rc2/arch/x86/pci/common.c      2008-05-12 11:22:05.000000000 -0700
> >  > >  @@ -121,6 +121,21 @@ void __init dmi_check_skip_isa_align(voi
> >  > >         dmi_check_system(can_skip_pciprobe_dmi_table);
> >  > >   }
> >  > >
> >  > >  +static void __devinit pcibios_fixup_device_resources(struct pci_dev *dev)
> >  > >  +{
> >  > >  +       struct resource *rom_r = &dev->resource[PCI_ROM_RESOURCE];
> >  > >  +
> >  > >  +       if (pci_probe & PCI_NOASSIGN_ROMS) {
> >  > >  +               if (rom_r->parent)
> >  > >  +                       return;
> >  > >  +               if (rom_r->start) {
> >  > >  +                       /* we deal with BIOS assigned ROM later */
> >  > >  +                       return;
> >  > >  +               }
> >  > >  +               rom_r->start = rom_r->end = rom_r->flags = 0;
> >  > >  +       }
> >  > >  +}
> >  > >  +
> >  > >   /*
> >  > >   *  Called after each bus is probed, but before its children
> >  > >   *  are examined.
> >  > >  @@ -128,7 +143,11 @@ void __init dmi_check_skip_isa_align(voi
> >  > >
> >  > >   void __devinit  pcibios_fixup_bus(struct pci_bus *b)
> >  > >   {
> >  > >  +       struct pci_dev *dev;
> >  > >  +
> >  > >         pci_read_bridge_bases(b);
> >  > >  +       list_for_each_entry(dev, &b->devices, bus_list)
> >  > >  +               pcibios_fixup_device_resources(dev);
> >  > >   }
> >  >
> >  > or put check
> >  > +       if (pci_probe & PCI_NOASSIGN_ROMS) {
> >  >
> >  > out of loop?
> >
> >  I could certainly do that but I had intended that the new
> >  pcibios_fixup_device_resources function act as a container where
> >  other kinds of fixups could be added later.  Do you (or others)
> >  think the additional cycles consumed by this approach are an
> >  issue here?
> 
> ok, then wonder if we can don't assign roms for x86_64 by default.

No, I don't think so.  ..at least not by me! :)

There were some lkml/linux-pci visible discussions back in
November-December of last year where I floated the idea
of making PCI expansion ROM memory non-assignment the default:
  http://marc.info/?l=linux-kernel&m=119742188215024&w=2
  http://marc.info/?l=linux-kernel&m=119689499508369&w=2
I did not hear any objections so I went ahead and submitted
the change which entered mainline at 2.6.25-rc1 but it was
sternly evicted last week because of a reported regression
that it had caused:
  http://marc.info/?l=linux-kernel&m=121029093331908&w=2
Attachments to http://bugs.freedesktop.org/show_bug.cgi?id=15523
indicate that a 2.6.25-rc2 x86_64 kernel was being used.

> 
> can we use pci rom in 64 bit kernel?

Sorry, not sure if I understand this question.  I hope the
above answers it.

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

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