[PATCH v2 2/2] powerpc: update pci_controller.refcount for PCI devices and buses

[Mauricio Faria de Oliveira]

This patch employs the refcount in struct pci_controller to track
the references from PCI devices and buses (struct pci_dev/pci_bus).

In order to do that without modifying any PCI scan/probe approach
(e.g., PCI_PROBE_DEVTREE and PCI_PROBE_NORMAL), it leverages some
of the PCI arch-specific callback: pci_(add|release)_device() and
pci_(add|remove)_bus().

(a small change is required for PCI_PROBE_DEVTREE, which makes it
consistent with PCI_PROBE_NORMAL - the pci_dev should inherit the
parent pci_bus's phb pointer - see pci_setup_device() in probe.c)

This also has the advantage that locking for kref_(get|put)() is
satisfied by the 'pci_rescan_remove_lock' mutex, which is normal
practice for usage of the PCI subsystem - thus already in place.
More details added in comment on pcibios_release_device().

Signed-off-by: Mauricio Faria de Oliveira <mauricfo at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pci-bridge.h |  4 ++--
 arch/powerpc/kernel/pci-common.c      | 25 +++++++++++++++++++++++++
 arch/powerpc/kernel/pci-hotplug.c     | 29 +++++++++++++++++++++++++++++
 arch/powerpc/kernel/pci_of_scan.c     |  1 +
 4 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
index 6fde0a9..d10eee3 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h
@@ -131,8 +131,8 @@ struct pci_controller {
 
 	/*
 	 * Reference counting for the structures:
-	 * - TODO pci_dev
-	 * - TODO pci_bus
+	 * - pci_dev
+	 * - pci_bus
 	 * - TODO pci_dn
 	 * - TODO eeh_pe
 	 * - TODO eeh_dev
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 29b37d3..c55e9c0 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -1047,6 +1047,17 @@ static void pcibios_setup_device(struct pci_dev *dev)
 
 int pcibios_add_device(struct pci_dev *dev)
 {
+	struct pci_controller *phb = pci_bus_to_host(dev->bus);
+
+	pr_debug("PCI %s, pci_dev %p, phb %p\n", dev_name(&dev->dev), dev, phb);
+
+	if (!phb)
+		pr_warn("%s: PCI device %s has null PHB; refcount bug!",
+			__func__, dev_name(&dev->dev)); /* WARN_ON ahead */
+
+	/* locking: see comment on pcibios_release_device(). */
+	controller_get(phb);
+
 	/*
 	 * We can only call pcibios_setup_device() after bus setup is complete,
 	 * since some of the platform specific DMA setup code depends on it.
@@ -1062,6 +1073,20 @@ int pcibios_add_device(struct pci_dev *dev)
 	return 0;
 }
 
+void pcibios_add_bus(struct pci_bus *bus)
+{
+	struct pci_controller *phb = pci_bus_to_host(bus);
+
+	pr_debug("PCI %s, pci_bus %p, phb %p\n", dev_name(&bus->dev), bus, phb);
+
+	if (!phb)
+		pr_warn("%s: PCI bus %s has null PHB; refcount bug!",
+			__func__, dev_name(&bus->dev)); /* WARN_ON ahead */
+
+	/* locking: see comment on pcibios_release_device(). */
+	controller_get(phb);
+}
+
 void pcibios_setup_bus_devices(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
diff --git a/arch/powerpc/kernel/pci-hotplug.c b/arch/powerpc/kernel/pci-hotplug.c
index 2d71269..24d1a2a 100644
--- a/arch/powerpc/kernel/pci-hotplug.c
+++ b/arch/powerpc/kernel/pci-hotplug.c
@@ -55,15 +55,44 @@ EXPORT_SYMBOL_GPL(pci_find_bus_by_node);
  * @dev: PCI device
  *
  * The function is called before releasing the indicated PCI device.
+ *
+ * The locking for kref_get() and kref_put() of the PHB/pci_controller
+ * in pcibios_(add|release)_device() and pcibios_(add|remove)_bus() is
+ * satisfied by the pci_rescan_remove_lock mutex (required for rescan/
+ * remove paths of PCI devices/buses; the scan path doesn't require it,
+ * as there is only addition of devices/buses - no removal at all.)
  */
 void pcibios_release_device(struct pci_dev *dev)
 {
 	struct pci_controller *phb = pci_bus_to_host(dev->bus);
 
+	pr_debug("PCI %s, pci_dev %p, phb %p\n", dev_name(&dev->dev), dev, phb);
+
 	eeh_remove_device(dev);
 
 	if (phb->controller_ops.release_device)
 		phb->controller_ops.release_device(dev);
+
+	if (unlikely(!phb))
+		pr_warn("%s: PCI device %s has null PHB; refcount bug!",
+			__func__, dev_name(&dev->dev)); /* WARN_ON ahead */
+
+	/* locking: see comment on pcibios_release_device(). */
+	controller_put(phb);
+}
+
+void pcibios_remove_bus(struct pci_bus *bus)
+{
+	struct pci_controller *phb = pci_bus_to_host(bus);
+
+	pr_debug("PCI %s, pci_bus %p, phb %p\n", dev_name(&bus->dev), bus, phb);
+
+	if (unlikely(!phb))
+		pr_warn("%s: PCI bus %s has null PHB; refcount bug!",
+			__func__, dev_name(&bus->dev)); /* WARN_ON ahead */
+
+	/* locking: see comment on pcibios_release_device(). */
+	controller_put(phb);
 }
 
 /**
diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
index 526ac67..e6f0deb 100644
--- a/arch/powerpc/kernel/pci_of_scan.c
+++ b/arch/powerpc/kernel/pci_of_scan.c
@@ -142,6 +142,7 @@ struct pci_dev *of_create_pci_dev(struct device_node *node,
 	dev->devfn = devfn;
 	dev->multifunction = 0;		/* maybe a lie? */
 	dev->needs_freset = 0;		/* pcie fundamental reset required */
+	dev->sysdata = bus->sysdata;	/* inherit bus's phb for phb->refcount */
 	set_pcie_port_type(dev);
 
 	pci_dev_assign_slot(dev);
-- 
1.8.3.1