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    SubjectRe: [PATCH] PCI: boot parameter to avoid expansion ROM memory allocation
    On Tue, May 13, 2008 at 04:23:55PM -0700, Yinghai Lu wrote:
    > On Tue, May 13, 2008 at 3:28 PM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
    > > > > 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.
    > > >
    > > > ok, i think the driver could reload fw in the option rom to reset the
    > > > controlller in pci card.
    > > > i don't think there is other usage for the option rom after OS loaded,
    > > > except option rom contain other run-time code...
    > >
    > > On graphics devices it's used for more than just POSTing (in fact POSTing is
    > > the least of its uses these days). The ROM often contains tables describing
    > > the specific hardware configuration of a given board, including output
    > > information, extra supported modes, etc.
    > >
    > > On other devices, it can be used to store default settings (this is common for
    > > SCSI cards iirc, though I'm not sure how much Linux drivers use this info).
    > >
    > >
    > > > so could disable them all, and use pci-quirks to enable that for the
    > > > device/driver need it.
    > >
    > > Since it's probably only big systems that really need the extra address space,
    > > I'd rather to the opposite: allocate ROM space by default and let a boot
    > > option avoid it.
    >
    > that boot option will get rid of that ROM BAR for all devices...
    > big system could use several graphical cards that need ROM BAR and
    > several cards that don't need ROM BAR.

    Correct, not a perfect solution but better than we have right now.

    Gary

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


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