[Bugfix 1/2] x86, irq, PCI: Keep IRQ assignment for PCI devices during suspend/hibernation

[Jiang Liu <jiang.liu@linux.intel.com>]

Now IOAPIC driver dynamically allocates IRQ numbers for IOAPIC pins.
We need to keep IRQ assignment for PCI devices during suspend/hibernation,
otherwise it may cause failure of suspend/hibernation due to:
1) Device driver calls pci_enable_device() to allocate an IRQ number
   and register interrupt handler on the returned IRQ.
2) Device driver's suspend callback calls pci_disable_device() and
   release assigned IRQ in turn.
3) Device driver's resume callback calls pci_enable_device() to
   allocate IRQ number again. A different IRQ number may be assigned
   by IOAPIC driver this time.
4) Now the hardware delivers interrupt to the new IRQ but interrupt
   handler is still registered against the old IRQ, so it breaks
   suspend/hibernation.

To fix this issue, we keep IRQ assignment during suspend/hibernation.
Flag pci_dev.dev.power.is_prepared is used to detect that
pci_disable_device() is called during suspend/hibernation.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
Hi Borislav,
	Could you please help to review the patch again since I have
made changes against the previous version?
Regards!
Gerry
---
 arch/x86/pci/intel_mid_pci.c |    2 +-
 arch/x86/pci/irq.c           |    3 ++-
 drivers/acpi/pci_irq.c       |    4 ++++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/pci/intel_mid_pci.c b/arch/x86/pci/intel_mid_pci.c
index 09fece368592..3865116c51fb 100644
--- a/arch/x86/pci/intel_mid_pci.c
+++ b/arch/x86/pci/intel_mid_pci.c
@@ -229,7 +229,7 @@ static int intel_mid_pci_irq_enable(struct pci_dev *dev)
 
 static void intel_mid_pci_irq_disable(struct pci_dev *dev)
 {
-	if (dev->irq > 0)
+	if (!dev->dev.power.is_prepared && dev->irq > 0)
 		mp_unmap_irq(dev->irq);
 }
 
diff --git a/arch/x86/pci/irq.c b/arch/x86/pci/irq.c
index 748cfe8ab322..bc1a2c341891 100644
--- a/arch/x86/pci/irq.c
+++ b/arch/x86/pci/irq.c
@@ -1256,7 +1256,8 @@ static int pirq_enable_irq(struct pci_dev *dev)
 
 static void pirq_disable_irq(struct pci_dev *dev)
 {
-	if (io_apic_assign_pci_irqs && dev->irq) {
+	if (io_apic_assign_pci_irqs && !dev->dev.power.is_prepared &&
+	    dev->irq) {
 		mp_unmap_irq(dev->irq);
 		dev->irq = 0;
 	}
diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
index 6ba463ceccc6..c96887d5289e 100644
--- a/drivers/acpi/pci_irq.c
+++ b/drivers/acpi/pci_irq.c
@@ -481,6 +481,10 @@ void acpi_pci_irq_disable(struct pci_dev *dev)
 	if (!pin)
 		return;
 
+	/* Keep IOAPIC pin configuration when suspending */
+	if (dev->dev.power.is_prepared)
+		return;
+
 	entry = acpi_pci_irq_lookup(dev, pin);
 	if (!entry)
 		return;
-- 
1.7.10.4