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    SubjectRe: pci_restore_state
    On Sun, 04 Jun 2006 06:13:30 -0400
    Ryan Lortie <desrt@desrt.ca> wrote:

    > Currently pci_restore_state() (drivers/pci/pci.c) restores the PCI state
    > by copying in the saved PCI configuration space, a dword at a time,
    > starting from 0 up to 15.
    >
    > This causes a crash when my Macbook resumes from sleep (specifically,
    > when restoring the configuration space of the PCI bridge).
    >
    > Reading the PCI specification, the register at dword 1 (ie: bytes 4-7)
    > is split half and half between status and command words. The command
    > word effectively controls the way which the PCI device interacts with
    > the system. If it is 0, the device is logically disconnected from the
    > bus (PCI Local Bus Specification Revision 2.2, 6.2.2 "Device
    > Control").
    >
    > When a device first powers up, the command register value is normally
    > zero (and is zero in my specific case).
    >
    > The problem with the way that the PCI state is currently restored is
    > that the write to the command register logically reconnects the device
    > to the bus before the rest of the configuration space has been filled
    > in.
    >
    > My Macbook crashes on resume.
    >
    > If I reverse the for loop to start from 15 and count down to 0, then the
    > majority of the configuration space is filled in _before_ the command
    > word is modified. No crash.

    We have a patch pending which will do that.

    http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/gregkh-03-pci/pci-reverse-pci-config-space-restore-order.patch

    The present plan will be to get this into 2.6.18.
    -
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