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From: Scott Wood <scottwood@freescale.com>
To: Sethi Varun-B16395 <B16395@freescale.com>
Cc: Wood Scott-B07421 <B07421@freescale.com>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	Yoder Stuart-B08248 <B08248@freescale.com>
Subject: Re: pci overmapping
Date: Thu, 2 May 2013 13:19:30 -0500	[thread overview]
Message-ID: <1367518770.24411.13@snotra> (raw)
In-Reply-To: <C5ECD7A89D1DC44195F34B25E172658D4D3E5A@039-SN2MPN1-011.039d.mgd.msft.net> (from B16395@freescale.com on Thu May  2 13:09:53 2013)

On 05/02/2013 01:09:53 PM, Sethi Varun-B16395 wrote:
>=20
>=20
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Thursday, May 02, 2013 10:44 PM
> > To: Yoder Stuart-B08248
> > Cc: galak@kernel.crashing.org; Sethi Varun-B16395; linuxppc-
> > dev@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 =20
> 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 =20
> 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 =20
> physical support (outbound window address would be high order 36 bit =20
> value), right?

Not necessarily -- it depends on what the bus addresses are, not the =20
host addresses.

-Scott=

  reply	other threads:[~2013-05-02 18:19 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-02 17:05 pci overmapping Yoder Stuart-B08248
2013-05-02 17:13 ` Scott Wood
2013-05-02 18:09   ` Sethi Varun-B16395
2013-05-02 18:19     ` Scott Wood [this message]
2013-05-03  5:29       ` Sethi Varun-B16395

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