[Patch v2 21/23] x86/PCI: Refine the way to release PCI IRQ resources

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

Some PCI device drivers assume that pci_dev->irq won't change after
calling pci_disable_device() and pci_enable_device() during suspend and
resume.

Commit c03b3b0738a5 ("x86, irq, mpparse: Release IOAPIC pin when
PCI device is disabled") frees PCI IRQ resources when pci_disable_device()
is called and reallocate IRQ resources when pci_enable_device() is
called again. This breaks above assumption. So commit 3eec595235c1
("x86, irq, PCI: Keep IRQ assignment for PCI devices during
suspend/hibernation") and 9eabc99a635a ("x86, irq, PCI: Keep IRQ
assignment for runtime power management") fix the issue by avoiding
freeing/reallocating IRQ resources during PCI device suspend/resume.
They achieve this by checking dev.power.is_prepared and
dev.power.runtime_status.  PM maintainer, Rafael, then pointed out that
it's really an ugly fix which leaking PM internal state information to
IRQ subsystem.

Recently David Vrabel <david.vrabel@citrix.com> also reports an
regression in pciback driver caused by commit cffe0a2b5a34 ("x86, irq:
Keep balance of IOAPIC pin reference count"). Please refer to:
http://lkml.org/lkml/2015/1/14/546

So this patch refine the way to release PCI IRQ resources. Instead of
releasing PCI IRQ resources in pci_disable_device()/
pcibios_disable_device(), we now release it at driver unbinding
notification BUS_NOTIFY_UNBOUND_DRIVER. In other word, we only release
PCI IRQ resources when there's no driver bound to the PCI device, and
it keeps the assumption that pci_dev->irq won't through multiple
invocation of pci_enable_device()/pci_disable_device().

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 arch/x86/include/asm/pci_x86.h |    2 --
 arch/x86/pci/common.c          |   30 ++++++++++++++++++++++++++++--
 arch/x86/pci/intel_mid_pci.c   |    4 ++--
 arch/x86/pci/irq.c             |   15 +--------------
 drivers/acpi/pci_irq.c         |    9 +--------
 5 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
index 164e3f8d3c3d..fa1195dae425 100644
--- a/arch/x86/include/asm/pci_x86.h
+++ b/arch/x86/include/asm/pci_x86.h
@@ -93,8 +93,6 @@ extern raw_spinlock_t pci_config_lock;
 extern int (*pcibios_enable_irq)(struct pci_dev *dev);
 extern void (*pcibios_disable_irq)(struct pci_dev *dev);
 
-extern bool mp_should_keep_irq(struct device *dev);
-
 struct pci_raw_ops {
 	int (*read)(unsigned int domain, unsigned int bus, unsigned int devfn,
 						int reg, int len, u32 *val);
diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 7b20bccf3648..99f15ed19f38 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -497,6 +497,25 @@ void __init pcibios_set_cache_line_size(void)
 	}
 }
 
+static int pci_irq_notifier(struct notifier_block *nb, unsigned long action,
+			    void *data)
+{
+	struct pci_dev *dev = to_pci_dev(data);
+
+	if (action != BUS_NOTIFY_UNBOUND_DRIVER)
+		return NOTIFY_DONE;
+
+	if (pcibios_disable_irq)
+		pcibios_disable_irq(dev);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block pci_irq_nb = {
+	.notifier_call = pci_irq_notifier,
+	.priority = INT_MIN,
+};
+
 int __init pcibios_init(void)
 {
 	if (!raw_pci_ops) {
@@ -509,6 +528,9 @@ int __init pcibios_init(void)
 
 	if (pci_bf_sort >= pci_force_bf)
 		pci_sort_breadthfirst();
+
+	bus_register_notifier(&pci_bus_type, &pci_irq_nb);
+
 	return 0;
 }
 
@@ -669,8 +691,12 @@ int pcibios_enable_device(struct pci_dev *dev, int mask)
 
 void pcibios_disable_device (struct pci_dev *dev)
 {
-	if (!pci_dev_msi_enabled(dev) && pcibios_disable_irq)
-		pcibios_disable_irq(dev);
+	/*
+	 * Some device drivers assume dev->irq won't change after calling
+	 * pci_disable_device(). So delay releasing of IRQ resource to driver
+	 * unbinding time. Otherwise it will break PM subsystem and drivers
+	 * like xen-pciback etc.
+	 */
 }
 
 int pci_ext_cfg_avail(void)
diff --git a/arch/x86/pci/intel_mid_pci.c b/arch/x86/pci/intel_mid_pci.c
index 44b9271580b5..95c2471f6819 100644
--- a/arch/x86/pci/intel_mid_pci.c
+++ b/arch/x86/pci/intel_mid_pci.c
@@ -234,10 +234,10 @@ static int intel_mid_pci_irq_enable(struct pci_dev *dev)
 
 static void intel_mid_pci_irq_disable(struct pci_dev *dev)
 {
-	if (!mp_should_keep_irq(&dev->dev) && dev->irq_managed &&
-	    dev->irq > 0) {
+	if (dev->irq_managed && dev->irq > 0) {
 		mp_unmap_irq(dev->irq);
 		dev->irq_managed = 0;
+		dev->irq = 0;
 	}
 }
 
diff --git a/arch/x86/pci/irq.c b/arch/x86/pci/irq.c
index 5dc6ca5e1741..e71b3dbd87b8 100644
--- a/arch/x86/pci/irq.c
+++ b/arch/x86/pci/irq.c
@@ -1256,22 +1256,9 @@ static int pirq_enable_irq(struct pci_dev *dev)
 	return 0;
 }
 
-bool mp_should_keep_irq(struct device *dev)
-{
-	if (dev->power.is_prepared)
-		return true;
-#ifdef CONFIG_PM
-	if (dev->power.runtime_status == RPM_SUSPENDING)
-		return true;
-#endif
-
-	return false;
-}
-
 static void pirq_disable_irq(struct pci_dev *dev)
 {
-	if (io_apic_assign_pci_irqs && !mp_should_keep_irq(&dev->dev) &&
-	    dev->irq_managed && dev->irq) {
+	if (io_apic_assign_pci_irqs && dev->irq_managed && dev->irq) {
 		mp_unmap_irq(dev->irq);
 		dev->irq = 0;
 		dev->irq_managed = 0;
diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
index b1def411c0b8..e7f718d6918a 100644
--- a/drivers/acpi/pci_irq.c
+++ b/drivers/acpi/pci_irq.c
@@ -485,14 +485,6 @@ void acpi_pci_irq_disable(struct pci_dev *dev)
 	if (!pin || !dev->irq_managed || dev->irq <= 0)
 		return;
 
-	/* Keep IOAPIC pin configuration when suspending */
-	if (dev->dev.power.is_prepared)
-		return;
-#ifdef	CONFIG_PM
-	if (dev->dev.power.runtime_status == RPM_SUSPENDING)
-		return;
-#endif
-
 	entry = acpi_pci_irq_lookup(dev, pin);
 	if (!entry)
 		return;
@@ -513,5 +505,6 @@ void acpi_pci_irq_disable(struct pci_dev *dev)
 	if (gsi >= 0) {
 		acpi_unregister_gsi(gsi);
 		dev->irq_managed = 0;
+		dev->irq = 0;
 	}
 }
-- 
1.7.10.4