PCI BAR initialisation..?

ashish anand ashisha at india.infogain.com
Thu Jul 12 11:47:50 EST 2001

I have mpc107 pci-host bridge.
motherboard is sandpoint + mcp750 processor.
pci_config_access method is indirect and config_address is 0xfec00000
config_data is 0xfee00000 rather than 0xcfc and 0xcf8.

i wonder if it would have been a case of memory reordering in that case
In bios how can we always believe on resource assignment of devices.
does it just a matter of chance that when we assign through bios this
reordering issue doesn't affect us..

Paul Mackerras wrote:
> ashish anand writes:
> > But by any chance if somebody has come across a random feature of pci BAR.
> > that is if you write the required pci addresses in BAR after writing 0xffffffff and
> > reading it back , and to confirm if the actual value has reached the BAR , we read it again
> > but then it returns funny values.
> >
> > more surprisingly if i move the code in some other function then everything behaves correctly.
> > I am more then sure that nothing relevant is happening betwen two places.
> Hmmm, that sounds like maybe the config space reads and writes are
> getting reordered, which would be a Bad Thing.
> What sort of PCI host bridge does your system have?
> If you place an mb() call after each pci config read or write, does
> that fix the problem?
> Paul.

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