[PATCH v2 19/27] pci: PCIe driver for Marvell Armada 370/XP systems

[Russell King - ARM Linux]

On Wed, Jan 30, 2013 at 01:03:44PM +0100, Thierry Reding wrote:
> On Wed, Jan 30, 2013 at 11:32:46AM +0000, Russell King - ARM Linux wrote:
> > On Mon, Jan 28, 2013 at 07:56:28PM +0100, Thomas Petazzoni wrote:
> > > +static resource_size_t mvebu_pcie_align_resource(struct pci_dev *dev,
> > > +						 const struct resource *res,
> > > +						 resource_size_t start,
> > > +						 resource_size_t size,
> > > +						 resource_size_t align)
> > > +{
> > > +	if (!(res->flags & IORESOURCE_IO))
> > > +		return start;
> > > +
> > > +	/*
> > > +	 * The I/O regions must be 64K aligned, because the
> > > +	 * granularity of PCIe I/O address decoding windows is 64 K
> > > +	 */
> > > +	return round_up(start, SZ_64K);
> > > +}
> > 
> > You do realise that this will result in all PCI I/O BARs being rounded
> > up to 64K.
> > 
> > I've just been digging through the PCI code and have come across a
> > function - pcibios_window_alignment() - which the PCI code allows to be
> > overriden which allows you to increase the alignment requirement of
> > bridge windows.  It takes the PCI bus and window type as arguments.
> > 
> > I'd suggest using that, and checking whether the bus which is passed
> > corresponds with a bus which gives you problems, so that you don't
> > impose the 64K requirement on downstream bridges.
> 
> That approach isn't going to work very well with multi-platform, though,
> since the function can only be overridden on a per-architecture basis.

The same can be said of all the various other functions which the PCI
stuff expects the arch to provide, yet we seem to cope just fine...