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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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