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    SubjectRe: [PATCH] kexec: fix pci device initialization fail after kexec (2.6.23-rc2). (Related to e1000 doesn't resume properly from standby)
    2007/8/6, Rafael J. Wysocki <rjw@sisk.pl>:
    > On Monday, 6 August 2007 15:42, Joonwoo Park wrote:
    > > Hi.
    > > I think that the pci_set_power_state() has bug.
    > > The specification says that some delays is required.
    >
    > And they are in place, AFAICS (from drivers/pci/pci.c):
    >
    > /* Mandatory power management transition delays */
    > /* see PCI PM 1.1 5.6.1 table 18 */
    > if (state == PCI_D3hot || dev->current_state == PCI_D3hot)
    > msleep(pci_pm_d3_delay);
    > else if (state == PCI_D2 || dev->current_state == PCI_D2)
    > udelay(200);
    >

    The problem is occurred when state is 'PCI_D0', so those codes can't cover it.
    But pci pm specification 5.4.1 says that when programmed to D0 the
    equivalent of a warm reset, delay for the duration of the D3hot to D0
    Uninitialized state
    transition (10ms) to pci signal drivers remain disabled is required.

    > > Simon, please can I know whether it works to you?
    > > It is seems to the things are related.
    > >
    > > Joonwoo Park.
    > >
    > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
    > > index 37c00f6..9f78064 100644
    > > --- a/drivers/pci/pci.c
    > > +++ b/drivers/pci/pci.c
    > > @@ -493,8 +493,14 @@ pci_set_power_state(struct pci_dev *dev, pci_power_t state)
    > > * restore at least the BARs so that the device will be
    > > * accessible to its driver.
    > > */
    > > - if (need_restore)
    > > + if (need_restore) {
    > > + /* The specification also says that "Must ensure that all of
    > > + * its PCI signal drivers remain disabled for the duration of
    > > + * the D3hot to D0 Uninitialized state transition".
    > > + */
    > > + msleep(10);
    >
    > It's too late for the delay.
    >

    How about this?

    diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
    index 37c00f6..974dd04 100644
    --- a/drivers/pci/pci.c
    +++ b/drivers/pci/pci.c
    @@ -471,6 +471,8 @@ pci_set_power_state(struct pci_dev *dev, pci_power_t state)
    msleep(pci_pm_d3_delay);
    else if (state == PCI_D2 || dev->current_state == PCI_D2)
    udelay(200);
    + else if (state == PCI_D0)
    + msleep(10);

    /*
    * Give firmware a chance to be called, such as ACPI _PRx, _PSx

    > > pci_restore_bars(dev);
    > > + }
    > >
    > > return 0;
    > > }
    >
    > Greetings,
    > Rafael
    >
    >
    > --
    > "Premature optimization is the root of all evil." - Donald Knuth
    >

    Thanks,
    Joonwoo Park.
    -
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