On Wed, Aug 08, 2007 at 07:50:44PM -0500, Nathan Lynch wrote:
> The maple pci configuration space write methods read the written
> location immediately after the write is performed, presumably in order
> to flush the write. However, configuration space writes are not
> allowed to be posted, making these reads gratuitous.
It might be worth checking that there isn't a particular reason for
these. Just because posting writes are forbidden doesn't mean a
particular bridge won't screw it up...
> Furthermore,
> this behavior potentially causes us to violate the PCI PM spec when
> changing between e.g. D0 and D3 states, because a delay of up to 10ms
> may be required before the OS accesses configuration space after the
> write which initiates the transition. It definitely causes a system
> hang for me with a Broadcom 5721 PCIE network adapter, which is fixed
> by this change.
>
> Remove the gratuitous reads from u3_agp_write_config,
> u3_ht_write_config, and u4_pcie_write_config.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
