pci overmapping

[Sethi Varun-B16395]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Thursday, May 02, 2013 10:44 PM
> To: Yoder Stuart-B08248
> Cc: galak at kernel.crashing.org; Sethi Varun-B16395; linuxppc-
> dev at lists.ozlabs.org
> Subject: Re: pci overmapping
> 
> On 05/02/2013 12:05:42 PM, Yoder Stuart-B08248 wrote:
> > Kumar,
> >
> > In fsl_pci.c there is a change you made a while back:
> >   "powerpc/fsl: Setup PCI inbound window based on actual amount of
> > memory"
> >
> > ...and there is this comment in the code:
> >
> >     /* PCIe can overmap inbound & outbound since RX & TX are separated
> > */
> >     if (early_find_capability(hose, 0, 0, PCI_CAP_ID_EXP)) {
> >
> > You are implying that PCIe can overmap and PCI can't.  Why is
> > that?   (I'm assuming that 'overmap' means that inbound window
> > can extend beyond the end of ram.)
> 
> Shouldn't the concern be whether we're overlapping outbound, not merely
> whether we go beyond the end of RAM?
> 
> And couldn't inbound/outbound overlap be an issue even on PCIe, if
> there's a PCI bridge underneath it?
I believe that the overlap problem would be avoided in case of 36 bit physical support (outbound window address would be high order 36 bit value), right?

-Varun