Re: [PATCH 1/1] ia64/pci: set mmio decoding on for some host bridge

[ZhenHua]

Hi Bjorn,
Thank you for reviewing this patch. I have created a new one and sent it 
out.
And your questions are answered in that new wmail.

Regards
ZhenHua

On 07/09/2013 04:35 AM, Bjorn Helgaas wrote:
> On Sun, Jul 7, 2013 at 6:16 PM, Li, Zhen-Hua <zhen-hual@xxxxxx> wrote:
> > On some IA64 platforms with intel PCI bridge, for example, HP BL890c i2
> > with  Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port,
> > when kernel tries to disable the mmio decoding on the PCI bridge devices,
> > kernel may crash.
> >
> > And in the comment of function quirk_mmio_always_on, it also says:
> > "But doing so (disable the mmio decoding) may cause problems on host bridge
> >   and perhaps other key system devices"
> >
> > So, for these PCI bridges,  dev->mmio_always_on bit should be set to 1.
> >
> >
> > Signed-off-by: Li, Zhen-Hua <zhen-hual@xxxxxx>
> > ---
> >   drivers/pci/quirks.c |   15 +++++++++++++++
> >   1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index e85d230..24b8024 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -44,6 +44,21 @@ static void quirk_mmio_always_on(struct pci_dev *dev)
> >   DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_ANY_ID, PCI_ANY_ID,
> >                                  PCI_CLASS_BRIDGE_HOST, 8, quirk_mmio_always_on);
> >
> > +#ifdef CONFIG_IA64
> > +/*
> > + * On some IA64 platforms, for some intel PCI bridge devices, for example,
> > + * the Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port,
> > + * disable the mmio decoding on these devices may cause system crash.
> > + * So dev->mmio_always_on bit should be set to 1.
> > + */
> > +static void quirk_mmio_on_intel_pcibridge(struct pci_dev *dev)
> > +{
> > +       dev->mmio_always_on = 1;
> > +}
> > +DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_ANY_ID, PCI_ANY_ID,
> > +                       PCI_CLASS_BRIDGE_PCI, 8, quirk_mmio_on_intel_pcibridge);
> > +#endif
> The changelog and comment suggest an issue specific to Intel
> 5520/5500/X58, but the patch sets mmio_always_on for *all* PCI
> bridges.
>
> It claims to be specific to ia64 (and is only compiled there), but the
> chipset is also used for x86.  You need to explain why the problem
> only affects ia64.
>
> Bjorn

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