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

[Thierry Reding]

On Wed, Jan 30, 2013 at 03:19:34PM +0000, Russell King - ARM Linux wrote:
> On Wed, Jan 30, 2013 at 03:08:56PM +0000, Russell King - ARM Linux wrote:
> > 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...
> 
> And this (untested) is how it's done:
> 
>  arch/arm/include/asm/mach/pci.h |    1 +
>  arch/arm/kernel/bios32.c        |    8 ++++++++
>  2 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mach/pci.h b/arch/arm/include/asm/mach/pci.h
> index db9fedb..bba0cf3 100644
> --- a/arch/arm/include/asm/mach/pci.h
> +++ b/arch/arm/include/asm/mach/pci.h
> @@ -29,6 +29,7 @@ struct hw_pci {
>  	void		(*postinit)(void);
>  	u8		(*swizzle)(struct pci_dev *dev, u8 *pin);
>  	int		(*map_irq)(const struct pci_dev *dev, u8 slot, u8 pin);
> +	resource_size_t	(*window_align)(struct pci_bus *, unsigned long);
>  };
>  
>  /*
> diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c
> index 379cf32..32c3bd9 100644
> --- a/arch/arm/kernel/bios32.c
> +++ b/arch/arm/kernel/bios32.c
> @@ -581,6 +581,14 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res,
>  	return start;
>  }
>  
> +resource_size_t pcibios_window_alignment(struct pci_bus *bus,
> +					 unsigned long type)
> +{
> +	struct pci_sys_data *sys = bus->sysdata;
> +
> +	return sys->window_alignment ? sys->window_alignment(bus, type) : 1;
> +}
> +
>  /**
>   * pcibios_enable_device - Enable I/O and memory.
>   * @dev: PCI device to be enabled

Yes, something like that'll work. I had been under the impression that
what you proposed was overriding pcibios_window_alignment() for Marvell
only.

Thierry
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