Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754062AbZIUVgN (ORCPT ); Mon, 21 Sep 2009 17:36:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753573AbZIUVgK (ORCPT ); Mon, 21 Sep 2009 17:36:10 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:59964 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753096AbZIUVgJ (ORCPT ); Mon, 21 Sep 2009 17:36:09 -0400 From: "Rafael J. Wysocki" To: Jesse Barnes Subject: [PATCH] PCI PM: Read device power state from register after updating it (rev. 2) Date: Mon, 21 Sep 2009 23:37:01 +0200 User-Agent: KMail/1.12.1 (Linux/2.6.31-rjw; KDE/4.3.1; x86_64; ; ) Cc: LKML , Linux PCI , pm list MIME-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <200909212337.01812.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2220 Lines: 48 From: Rafael J. Wysocki After attempting to change the power state of a PCI device pci_raw_set_power_state() doesn't check if the value it wrote into the device's PCI_PM_CTRL register has been stored in there, but unconditionally modifies the device's current_state field to reflect the change. This may cause problems to happen if the power state of the device hasn't been changed in fact, because it will make the PCI PM core think that the device is in a power state it really is not in. To prevent such situations from happening modify pci_raw_set_power_state() so that it reads the device's PCI_PM_CTRL register after writing into it and uses the value read from the register to update the device's current_state field. Also make it print a message saying that the device refused to change its power state as requested (returning an error code in such cases would cause suspend regressions to appear on some systems, where device drivers' suspend routines return error codes if pci_set_power_state() fails). Signed-off-by: Rafael J. Wysocki --- drivers/pci/pci.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) Index: linux-2.6/drivers/pci/pci.c =================================================================== --- linux-2.6.orig/drivers/pci/pci.c +++ linux-2.6/drivers/pci/pci.c @@ -513,7 +513,12 @@ static int pci_raw_set_power_state(struc else if (state == PCI_D2 || dev->current_state == PCI_D2) udelay(PCI_PM_D2_DELAY); - dev->current_state = state; + pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); + dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); + /* Return error code if we have failed to change the state */ + if (dev->current_state != state) + dev_info(&dev->dev, "Refused to change power state, " + "currently in D%d\n", dev->current_state); /* According to section 5.4.1 of the "PCI BUS POWER MANAGEMENT * INTERFACE SPECIFICATION, REV. 1.2", a device transitioning -- 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/