On Friday 09 October 2009, Bjorn Helgaas wrote:
> On Thursday 08 October 2009 04:52:48 pm Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@xxxxxxx>
> >
> > Add function pci_check_pme_status() that will check the PME status
> > bit of given device and clear it along with the PME enable bit. It
> > will be necessary for PCI run-time power management.
> >
> > Based on a patch from Shaohua Li <shaohua.li@xxxxxxxxx>
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> > ---
> > drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++++++++
> > drivers/pci/pci.h | 1 +
> > 2 files changed, 36 insertions(+)
> >
> > Index: linux-2.6/drivers/pci/pci.h
> > ===================================================================
> > --- linux-2.6.orig/drivers/pci/pci.h
> > +++ linux-2.6/drivers/pci/pci.h
> > @@ -49,6 +49,7 @@ struct pci_platform_pm_ops {
> > extern int pci_set_platform_pm(struct pci_platform_pm_ops *ops);
> > extern void pci_update_current_state(struct pci_dev *dev, pci_power_t state);
> > extern void pci_disable_enabled_device(struct pci_dev *dev);
> > +extern bool pci_check_pme_status(struct pci_dev *dev);
> > extern void pci_pm_init(struct pci_dev *dev);
> > extern void platform_pci_wakeup_init(struct pci_dev *dev);
> > extern void pci_allocate_cap_save_buffers(struct pci_dev *dev);
> > Index: linux-2.6/drivers/pci/pci.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/pci/pci.c
> > +++ linux-2.6/drivers/pci/pci.c
> > @@ -1167,6 +1167,41 @@ int pci_set_pcie_reset_state(struct pci_
> > }
> >
> > /**
> > + * pci_check_pme_status - Check if given device has generated PME.
> > + * @dev: Device to check.
> > + *
> > + * Check the PME status of the device, clear PME status and PME enable. Return
> > + * 'true' if PME has been generated by the device (and hasn't been spurious) or
> > + * 'false' otherwise.
>
> This comment confuses me because it implies that we always clear PME enable,
> but that's not what the code does. If PME_STATUS is not asserted, the code
> doesn't write anything.
Well, that's a shortcut, perhaps going too far. It should say "clear PME
status and PME enable, if the PME status was set". Will fix.
> > + */
> > +bool pci_check_pme_status(struct pci_dev *dev)
> > +{
> > + int pmcsr_pos;
> > + u16 pmcsr;
> > + bool ret = false;
> > +
> > + if (!dev->pm_cap)
> > + return false;
> > +
> > + pmcsr_pos = dev->pm_cap + PCI_PM_CTRL;
> > + /* clear PME status and disable PME to avoid interrupt flood */
> > + pci_read_config_word(dev, pmcsr_pos, &pmcsr);
> > + if (!(pmcsr & PCI_PM_CTRL_PME_STATUS))
> > + return false;
> > +
> > + pmcsr |= PCI_PM_CTRL_PME_STATUS;
> > + /* Ignore spurious PME or clear PME enable if it's not spurious. */
> > + if (pmcsr & PCI_PM_CTRL_PME_ENABLE) {
> > + pmcsr &= ~PCI_PM_CTRL_PME_ENABLE;
> > + ret = true;
> > + }
> > +
> > + pci_write_config_word(dev, pmcsr_pos, pmcsr);
>
> I can't tell whether the comment or the code is what was intended,
The code. I'll fix the comment.
> but I think the following would be a clearer way to implement the
> comment:
>
> pci_read_config_word(..., &pmcsr);
> pci_write_config_word(..., (pmcsr | STATUS) & ~ENABLE);
>
> if ((pmcsr & ENABLE) && (pmcsr & STATUS))
> return true;
> return false;
Thanks,
Rafael
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