diff options
| -rw-r--r-- | drivers/pci/pci.c | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 54858838f09..485cfa9af2e 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1578,15 +1578,25 @@ void pci_pme_active(struct pci_dev *dev, bool enable) pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, pmcsr); - /* PCI (as opposed to PCIe) PME requires that the device have - its PME# line hooked up correctly. Not all hardware vendors - do this, so the PME never gets delivered and the device - remains asleep. The easiest way around this is to - periodically walk the list of suspended devices and check - whether any have their PME flag set. The assumption is that - we'll wake up often enough anyway that this won't be a huge - hit, and the power savings from the devices will still be a - win. */ + /* + * PCI (as opposed to PCIe) PME requires that the device have + * its PME# line hooked up correctly. Not all hardware vendors + * do this, so the PME never gets delivered and the device + * remains asleep. The easiest way around this is to + * periodically walk the list of suspended devices and check + * whether any have their PME flag set. The assumption is that + * we'll wake up often enough anyway that this won't be a huge + * hit, and the power savings from the devices will still be a + * win. + * + * Although PCIe uses in-band PME message instead of PME# line + * to report PME, PME does not work for some PCIe devices in + * reality. For example, there are devices that set their PME + * status bits, but don't really bother to send a PME message; + * there are PCI Express Root Ports that don't bother to + * trigger interrupts when they receive PME messages from the + * devices below. So PME poll is used for PCIe devices too. + */ if (dev->pme_poll) { struct pci_pme_device *pme_dev; |