Re: [PATCH 05/15] pci: resource assignment based on p2p alignment

[Ram Pai <linuxram@us.ibm.com>]

On Tue, Jul 17, 2012 at 08:38:18PM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2012-07-17 at 18:03 +0800, Ram Pai wrote:
> >         Lets say we passed that 'type' flag to size the minimum
> >         alignment constraints for that b_res.  And window_alignment(bus,
> >         type) of your platform  used that 'type' information to
> >         determine whether to use the alignment constraints of 32-bit
> >         window or 64-bit window.
> > 
> >         However, later when the b_res is actually allocated a resource,
> >         the pci_assign_resource() has no idea whether to allocate 32-bit
> >         window resource or 64-bit window resource, because the 'type'
> >         information is not captured anywhere in b_res.
> > 
> >         You would basically have a disconnect between what is sized and 
> >         what is allocated. Unless offcourse you pass that 'type' to
> >         the b_res->flags, which is currently not the case. 
> 
> Right, we ideally would need the core to query the alignment once per
> "apertures" it tries as a candidate to allocate a given resource... but
> that's for later.
> 
> For now we can probably live with giving out the max of the minimum
> alignment we support for M64 and our M32 segment size.

Its an approximation, which may not be terribly bad. But not comforting enough.

RP