linux-kernel - [PATCH] PCI / PM: Fix fallback to PCI_D0 in pci_platform_power

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Date:	Sat, 13 Apr 2013 01:58:17 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	"Benenati, Chris J" <chris.j.benenati@...el.com>
Subject: [PATCH] PCI / PM: Fix fallback to PCI_D0 in pci_platform_power_transition()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Commit b51306c (PCI: Set device power state to PCI_D0 for device
without native PM support) modified pci_platform_power_transition()
by adding code causing dev->current_state for devices that don't
support native PCI PM but are power-manageable by the platform to be
changed to PCI_D0 regardless of the value returned by the preceding
platform_pci_set_power_state().  In particular, that also is done
if the platform_pci_set_power_state() has been successful, which
causes the correct power state of the device set by
pci_update_current_state() in that case to be overwritten by PCI_D0.

Fix that mistake by making the fallback to PCI_D0 only happen if
the platform_pci_set_power_state() has returned an error.

Reported-by: Chris J. Benenati <chris.j.benenati@...el.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: <stable@...r.kernel.org>
---
 drivers/pci/pci.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -646,8 +646,7 @@ static int pci_platform_power_transition
 		error = platform_pci_set_power_state(dev, state);
 		if (!error)
 			pci_update_current_state(dev, state);
-		/* Fall back to PCI_D0 if native PM is not supported */
-		if (!dev->pm_cap)
+		else if (!dev->pm_cap) /* Fall back to PCI_D0 */
 			dev->current_state = PCI_D0;
 	} else {
 		error = -ENODEV;

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