linux-kernel - [PATCH bugfix 3.9] PCI: Don't try to disable Bus Master on disconnected PCI devices

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Date:	Thu, 14 Mar 2013 18:49:37 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	linux-kernel@...r.kernel.org
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	kexec@...ts.infradead.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jeff Garzik <jgarzik@...ox.com>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: [PATCH bugfix 3.9] PCI: Don't try to disable Bus Master on
 disconnected PCI devices

This is fix for commit 7897e6022761ace7377f0f784fca059da55f5d71 from v3.9-rc1
("PCI: Disable Bus Master unconditionally in pci_device_shutdown()")
in turn that was fix for b566a22c23327f18ce941ffad0ca907e50a53d41 from v3.5-rc1
("PCI: disable Bus Master on PCI device shutdown")

Unfortunately fixing one bug uncovers another:
->shutdown() callback might switch device to deep sleep state.
PCI config space no longer available after that.

Link: https://lkml.org/lkml/2013/3/12/529
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
Reported-and-Tested-by: Vivek Goyal <vgoyal@...hat.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/pci/pci-driver.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 1fa1e48..79277fb 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -390,9 +390,10 @@ static void pci_device_shutdown(struct device *dev)
 
 	/*
 	 * Turn off Bus Master bit on the device to tell it to not
-	 * continue to do DMA
+	 * continue to do DMA. Don't touch devices in D3cold or unknown states.
 	 */
-	pci_clear_master(pci_dev);
+	if (pci_dev->current_state <= PCI_D3hot)
+		pci_clear_master(pci_dev);
 }
 
 #ifdef CONFIG_PM

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