[PATCH v2 1/2] powerpc: add refcount to struct pci_controller

[Mauricio Faria de Oliveira]

This commit introduces the 'refcount' field in struct pci_controller,
along with the corresponding functions 'controller_(get|put|free)()'.

The functions 'pcibios_(alloc|free)_controller()' are modified to use
that in a backwards compatible manner. (i.e., kfree(phb) is performed
when pcibios_free_controller() is called.)

So, this patch adds the infrastructure with no functional differences
to current users of pcibios_(alloc|free)_controller().  Notably, only
the pseries platform calls pcibios_free_controller() for some purpose
other than to release the pci_controller in case of errors just after
the call to pcibios_alloc_controller() (i.e., 'goto error' scenarios).

Signed-off-by: Mauricio Faria de Oliveira <mauri...@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pci-bridge.h | 15 +++++++++++
 arch/powerpc/kernel/pci-common.c      | 47 ++++++++++++++++++++++++++++++++---
 2 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/pci-bridge.h 
b/arch/powerpc/include/asm/pci-bridge.h
index b5e88e4..6fde0a9 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h
@@ -10,6 +10,7 @@
 #include <linux/pci.h>
 #include <linux/list.h>
 #include <linux/ioport.h>
+#include <linux/kref.h>
 
 struct device_node;
 
@@ -128,9 +129,23 @@ struct pci_controller {
        struct pci_dn *pci_data;
 #endif /* CONFIG_PPC64 */
 
+       /*
+        * Reference counting for the structures:
+        * - TODO pci_dev
+        * - TODO pci_bus
+        * - TODO pci_dn
+        * - TODO eeh_pe
+        * - TODO eeh_dev
+        */
+       struct kref refcount;
+
        void *private_data;
 };
 
+void controller_get(struct pci_controller *phb);
+void controller_put(struct pci_controller *phb);
+void controller_free(struct kref *kref);
+
 /* These are used for config access before all the PCI probing
    has been done. */
 extern int early_read_config_byte(struct pci_controller *hose, int bus,
diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 08afddf..29b37d3 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -114,6 +114,8 @@ struct pci_controller *pcibios_alloc_controller(struct 
device_node *dev)
        phb = zalloc_maybe_bootmem(sizeof(struct pci_controller), GFP_KERNEL);
        if (phb == NULL)
                return NULL;
+
+       kref_init(&phb->refcount); /* use first reference for hose_list entry */
        spin_lock(&hose_spinlock);
        phb->global_number = get_phb_number(dev);
        list_add_tail(&phb->list_node, &hose_list);
@@ -130,12 +132,53 @@ struct pci_controller *pcibios_alloc_controller(struct 
device_node *dev)
                PHB_SET_NODE(phb, nid);
        }
 #endif
+
+       pr_debug("PCI domain %d, phb %p, phb->is_dynamic %d\n",
+               phb->global_number, phb, phb->is_dynamic);
+
        return phb;
 }
 EXPORT_SYMBOL_GPL(pcibios_alloc_controller);
 
+void controller_get(struct pci_controller *phb)
+{
+       if (unlikely(!phb)) {
+               pr_warn("%s: null PHB; refcount bug!\n", __func__);
+               WARN_ON(1);
+       } else {
+               pr_debug("PCI domain %d, phb %p\n", phb->global_number, phb);
+               kref_get(&phb->refcount);
+       }
+}
+
+void controller_put(struct pci_controller *phb)
+{
+       if (unlikely(!phb)) {
+               pr_warn("%s: null PHB; refcount bug!\n", __func__);
+               WARN_ON(1);
+       } else {
+               pr_debug("PCI domain %d, phb %p\n", phb->global_number, phb);
+               kref_put(&phb->refcount, controller_free);
+       }
+}
+
+void controller_free(struct kref *kref)
+{
+       struct pci_controller *phb = container_of(kref, struct pci_controller,
+                                                       refcount);
+
+       pr_info("%s: PCI domain: %d, phb %p, phb->is_dynamic %d\n",
+               __func__, phb->global_number, phb, phb->is_dynamic);
+
+       if (phb->is_dynamic)
+               kfree(phb);
+}
+
 void pcibios_free_controller(struct pci_controller *phb)
 {
+       pr_debug("PCI domain %d, phb %p, phb->is_dynamic %d\n",
+               phb->global_number, phb, phb->is_dynamic);
+
        spin_lock(&hose_spinlock);
 
        /* Clear bit of phb_bitmap to allow reuse of this PHB number. */
@@ -143,10 +186,8 @@ void pcibios_free_controller(struct pci_controller *phb)
                clear_bit(phb->global_number, phb_bitmap);
 
        list_del(&phb->list_node);
+       controller_put(phb);
        spin_unlock(&hose_spinlock);
-
-       if (phb->is_dynamic)
-               kfree(phb);
 }
 EXPORT_SYMBOL_GPL(pcibios_free_controller);
 
-- 
1.8.3.1