From patchwork Fri Oct 26 05:07:51 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Huang, Ying" X-Patchwork-Id: 194354 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id A04542C00AA for ; Fri, 26 Oct 2012 16:08:17 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756182Ab2JZFIP (ORCPT ); Fri, 26 Oct 2012 01:08:15 -0400 Received: from mga03.intel.com ([143.182.124.21]:18107 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756165Ab2JZFIP (ORCPT ); Fri, 26 Oct 2012 01:08:15 -0400 Received: from azsmga001.ch.intel.com ([10.2.17.19]) by azsmga101.ch.intel.com with ESMTP; 25 Oct 2012 22:08:14 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.80,652,1344236400"; d="scan'208";a="209530386" Received: from yhuang-dev.sh.intel.com ([10.239.13.178]) by azsmga001.ch.intel.com with ESMTP; 25 Oct 2012 22:08:12 -0700 From: Huang Ying To: Bjorn Helgaas Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, "Rafael J. Wysocki" , Huang Ying , "Rafael J. Wysocki" Subject: PCI/PM: Add comments for PME poll support for PCIe Date: Fri, 26 Oct 2012 13:07:51 +0800 Message-Id: <1351228071-15161-1-git-send-email-ying.huang@intel.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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 --- 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 --- 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;