From 7897e6022761ace7377f0f784fca059da55f5d71 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Mon, 4 Feb 2013 15:55:58 +0400 Subject: [PATCH] PCI: Disable Bus Master unconditionally in pci_device_shutdown() Commit b566a22c23 ("PCI: disable Bus Master on PCI device shutdown") used pci_disable_device(), but that doesn't disable Bus Mastering unconditionally; we allow nested enable/disable calls, and only the last disable call actually does anything. This uses pci_clear_master() to unconditionally clear the Bus Master bit. Matthew Garrett and Alan Cox said (see LKML link below) that clearing Bus Master for all PCI devices may lead to unpredictable consequences: some devices ignores this bit and continue DMA, some of them hang after that or crash the whole system. But we're already trying to clear Bus Master in general because of b566a22c23; this merely deals with the cases where drivers haven't shut down the device correctly. [bhelgaas: changelog] Link: https://lkml.org/lkml/2012/6/6/278 Signed-off-by: Konstantin Khlebnikov Signed-off-by: Bjorn Helgaas Acked-by: Rafael J. Wysocki --- drivers/pci/pci-driver.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index f79cbcd3944b..dc5bdce63f12 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -392,7 +392,7 @@ 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 */ - pci_disable_device(pci_dev); + pci_clear_master(pci_dev); } #ifdef CONFIG_PM -- 2.20.1