> -----Original Message----- > From: Wood Scott-B07421 > Sent: Thursday, May 02, 2013 10:44 PM > To: Yoder Stuart-B08248 > Cc: ga...@kernel.crashing.org; Sethi Varun-B16395; linuxppc- > d...@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?
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