[PATCH v9 2/3] PCI: Add a macro to set default alignment for all PCI devices

[Bjorn Helgaas]

On Mon, Mar 27, 2017 at 09:25:50PM +1100, Benjamin Herrenschmidt wrote:
> On Mon, 2017-03-27 at 21:17 +1100, Michael Ellerman wrote:
> > > If so, is it acceptable to force that kernel to user 64K alignment
> > > even
> > > when it's running on non-PowerNV systems?
> > 
> > Probably, but I'm not sure TBH. Benh will know, I'll try and get his
> > attention.
> 
> Can we make the alignment PAGE_SIZE ? I think that should be ok as long
> as it doesn't try to re-allocate BARs for devices that have already
> been properly allocated by firmware (ie, PowerMac, if you mess around
> with the MacIO chip on these, bad things will happen).

I think this *will* change BARs even if they've already been allocated
by firmware, because it affects this path that is used for every
device:

  pci_device_add
    pci_reassigndev_resource_alignment
      pci_specified_resource_alignment
        align = PCIBIOS_DEFAULT_ALIGNMENT

I'm looking for an update that fixes the minor comment issues and
possibly addresses this PowerMac question.

Bjorn