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    SubjectRe: [patch 2.6.13-rc2] pci: restore BAR values from pci_set_power_state for D3hot->D0
    On Fri, Jul 08, 2005 at 02:34:56PM -0400, John W. Linville wrote:

    > Some PCI devices lose all configuration (including BARs) when
    > transitioning from D3hot->D0. This leaves such a device in an
    > inaccessible state. The patch below causes the BARs to be restored
    > when enabling such a device, so that its driver will be able to
    > access it.

    It might be useful to have this functionality exported to outside of
    the generic PCI code.

    There are a number of PCI boards that have their reset logic wired
    up wrong and lose their config space info (BARs) when you reset them.
    The Radisys ENP2611 PCI board is a good example -- it has its reset
    logic wired in such a way that if you reset the (ARM-based) CPU on
    the board, it also causes the 21555 nontransparent PCI bridge on the
    board to be reset, which makes it lose all its primary config space
    info (BARs, etc.) The IXP1200 CPU-based PCI cards (now obsolete)
    used to suffer from the same issue.

    This is currently worked around in the driver, which caches all BAR
    values when the module is first loaded, and detects when the card is
    reset and then writes back all BARs manually.

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