Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754889Ab2KEWPL (ORCPT ); Mon, 5 Nov 2012 17:15:11 -0500 Received: from mail-wg0-f44.google.com ([74.125.82.44]:61805 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753909Ab2KEWPI (ORCPT ); Mon, 5 Nov 2012 17:15:08 -0500 MIME-Version: 1.0 In-Reply-To: <3515628.KRd0S4T47k@vostro.rjw.lan> References: <1351228071-15161-1-git-send-email-ying.huang@intel.com> <3515628.KRd0S4T47k@vostro.rjw.lan> From: Bjorn Helgaas Date: Mon, 5 Nov 2012 15:14:46 -0700 Message-ID: Subject: Re: PCI/PM: Add comments for PME poll support for PCIe To: "Rafael J. Wysocki" Cc: Huang Ying , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, "Rafael J. Wysocki" Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3166 Lines: 68 On Fri, Oct 26, 2012 at 5:18 AM, Rafael J. Wysocki 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 >> Signed-off-by: Huang Ying > > Acked-by: Rafael J. Wysocki 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/