| Message ID | 1351228071-15161-1-git-send-email-ying.huang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Friday, October 26, 2012 01:07:51 PM Huang Ying wrote: > There are comments on why PME poll support is necessary for PCI > devices, but not for PCIe devices. That may lead to misunderstanding > that PME poll is only necessary for PCI devices. So add comments > related to PCIe PME poll to make it more clear. > > The content of comments comes from the changelog of commit: > > 379021d5c0899fcf9410cae4ca7a59a5a94ca769 > > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Signed-off-by: Huang Ying <ying.huang@intel.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/pci/pci.c | 28 +++++++++++++++++++--------- > 1 file changed, 19 insertions(+), 9 deletions(-) > > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -1578,15 +1578,25 @@ void pci_pme_active(struct pci_dev *dev, > > 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; >
On Fri, Oct 26, 2012 at 5:18 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote: > On Friday, October 26, 2012 01:07:51 PM Huang Ying wrote: >> There are comments on why PME poll support is necessary for PCI >> devices, but not for PCIe devices. That may lead to misunderstanding >> that PME poll is only necessary for PCI devices. So add comments >> related to PCIe PME poll to make it more clear. >> >> The content of comments comes from the changelog of commit: >> >> 379021d5c0899fcf9410cae4ca7a59a5a94ca769 >> >> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> Signed-off-by: Huang Ying <ying.huang@intel.com> > > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> I applied this to my pci/misc branch as v3.8 material. Thanks! >> --- >> drivers/pci/pci.c | 28 +++++++++++++++++++--------- >> 1 file changed, 19 insertions(+), 9 deletions(-) >> >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -1578,15 +1578,25 @@ void pci_pme_active(struct pci_dev *dev, >> >> 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; >> > -- > I speak only for myself. > Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1578,15 +1578,25 @@ void pci_pme_active(struct pci_dev *dev, 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;
There are comments on why PME poll support is necessary for PCI devices, but not for PCIe devices. That may lead to misunderstanding that PME poll is only necessary for PCI devices. So add comments related to PCIe PME poll to make it more clear. The content of comments comes from the changelog of commit: 379021d5c0899fcf9410cae4ca7a59a5a94ca769 Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Huang Ying <ying.huang@intel.com> --- drivers/pci/pci.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html