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@xxxxxxxxx>
> Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> 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.
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