[PATCH 3.8 027/166] PCI: Disable Bus Master only on kexec reboot

Kamal Mostafa
2014-01-15T21:50:41Z

From: Khalid Aziz <khalid.aziz@oracle.com>

commit 4fc9bbf98fd66f879e628d8537ba7c240be2b58e upstream.

Add a flag to tell the PCI subsystem that kernel is shutting down in
preparation to kexec a kernel. Add code in PCI subsystem to use this flag
to clear Bus Master bit on PCI devices only in case of kexec reboot.

This fixes a power-off problem on Acer Aspire V5-573G and likely other
machines and avoids any other issues caused by clearing Bus Master bit on
PCI devices in normal shutdown path. The problem was introduced by
b566a22c2332 ("PCI: disable Bus Master on PCI device shutdown").

This patch is based on discussion at
http://marc.info/?l=linux-pci&m=138425645204355&w=2

Link: https://bugzilla.kernel.org/show_bug.cgi?id=63861
Reported-by: Chang Liu <cl91tp@gmail.com>
Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Konstantin Khlebnikov <koct9i@gmail.com>
[ kamal: backport to 3.8 (context) ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/pci/pci-driver.c | 13 ++++++++++---
include/linux/kexec.h | 3 +++
kernel/kexec.c | 4 ++++
3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 8c1ecc5..66e919c 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -19,6 +19,7 @@
#include <linux/cpu.h>
#include <linux/pm_runtime.h>
#include <linux/suspend.h>
+#include <linux/kexec.h>
#include "pci.h"

struct pci_dynid {
@@ -388,11 +389,17 @@ static void pci_device_shutdown(struct device *dev)
pci_msi_shutdown(pci_dev);
pci_msix_shutdown(pci_dev);

+#ifdef CONFIG_KEXEC
/*
- * Turn off Bus Master bit on the device to tell it to not
- * continue to do DMA
+ * If this is a kexec reboot, turn off Bus Master bit on the
+ * device to tell it to not continue to do DMA. Don't touch
+ * devices in D3cold or unknown states.
+ * If it is not a kexec reboot, firmware will hit the PCI
+ * devices with big hammer and stop their DMA any way.
*/
- pci_disable_device(pci_dev);
+ if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot))
+ pci_clear_master(pci_dev);
+#endif
}

#ifdef CONFIG_PM
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d0b8458..9140056 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -197,6 +197,9 @@ extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
extern size_t vmcoreinfo_size;
extern size_t vmcoreinfo_max_size;

+/* flag to track if kexec reboot is in progress */
+extern bool kexec_in_progress;
+
int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base);
int crash_shrink_memory(unsigned long new_size);
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 5e4bd78..9533498 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -47,6 +47,9 @@ u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
size_t vmcoreinfo_size;
size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);

+/* Flag to indicate we are going to kexec a new kernel */
+bool kexec_in_progress = false;
+
/* Location of the reserved area for the crash kernel */
struct resource crashk_res = {
.name = "Crash kernel",
@@ -1569,6 +1572,7 @@ int kernel_kexec(void)
} else
#endif
{
+ kexec_in_progress = true;
kernel_restart_prepare(NULL);
printk(KERN_EMERG "Starting new kernel\n");
machine_shutdown();
--
1.8.3.2