[PATCH v2 3/3] PCI: ARM: add support for generic PCI host controller

Will Deacon will.deacon at arm.com
Thu Feb 13 14:53:17 EST 2014

On Thu, Feb 13, 2014 at 06:26:54PM +0000, Jason Gunthorpe wrote:
> On Thu, Feb 13, 2014 at 05:28:20PM +0100, Arnd Bergmann wrote:
> > > Huh?  The reg property clearly has the size in it (as shown in the
> > > example below).  I guess I was just asking for the description
> > > here to say what the size was for the 2 compatibles since its
> > > fixed and known.
> > 
> > It's still an open question whether the config space in the reg
> > property should cover all 256 buses or just the ones in the
> > bus-range. In the latter case, it would be variable (but
> > predictable) size.
> The 'describe the hardware principle' says the reg should be the
> entire available ECAM/CAM region the hardware is able to support.
> This may be less than 256 busses, as ECAM allows the implementor to
> select how many upper address bits are actually supported.

Ok, but the ECAM/CAM base always corresponds to bus 0, right?

> IMHO, the bus-range should be used to indicate the range of busses
> discovered by the firmware, but we have historically tweaked it to
> indicate the max range of bus numbers available on this bus (I think
> to support the hack where two physical PCI domains were roughly glued
> into a single Linux domain).

Ok, so this answers Kumar's point about the reg property. I'll augment it
with a size.


More information about the linux-arm-kernel mailing list