Further, when pseries lpars are migrated to a different machine we
perform a live update of our device tree to bring it into alignment with the
configuration of the new machine. The of_reconfig_notify trace point
provides a mechanism that can be turned for debuging the device tree
modifications with out having to build a custom kernel to get at the
DEBUG code introduced by commit 00aa3720.

The following trace events are provided: of_node_get, of_node_put,
of_node_release, and of_reconfig_notify. These trace points require a kernel
built with ftrace support to be enabled. In a typical environment where
debugfs is mounted at /sys/kernel/debug the entire set of tracepoints
can be set with the following:

  echo "of:*" > /sys/kernel/debug/tracing/set_event

or

  echo 1 > /sys/kernel/debug/tracing/of/enable

The following shows the trace point data from a DLPAR remove of a cpu
from a pseries lpar:

cat /sys/kernel/debug/tracing/trace | grep "POWER8@10"

cpuhp/23-147   [023] ....   128.324827:
        of_node_put: refcount=5, dn->full_name=/cpus/PowerPC,POWER8@10
cpuhp/23-147   [023] ....   128.324829:
        of_node_put: refcount=4, dn->full_name=/cpus/PowerPC,POWER8@10
cpuhp/23-147   [023] ....   128.324829:
        of_node_put: refcount=3, dn->full_name=/cpus/PowerPC,POWER8@10
cpuhp/23-147   [023] ....   128.324831:
        of_node_put: refcount=2, dn->full_name=/cpus/PowerPC,POWER8@10
   drmgr-7284  [009] ....   128.439000:
        of_node_put: refcount=1, dn->full_name=/cpus/PowerPC,POWER8@10
   drmgr-7284  [009] ....   128.439002:
        of_reconfig_notify: action=DETACH_NODE, dn->full_name=/cpus/PowerPC,POWER8@10,
                            prop->name=null, old_prop->name=null
   drmgr-7284  [009] ....   128.439015:
        of_node_put: refcount=0, dn->full_name=/cpus/PowerPC,POWER8@10
   drmgr-7284  [009] ....   128.439016:
        of_node_release: dn->full_name=/cpus/PowerPC,POWER8@10, dn->_flags=4

Signed-off-by: Tyrel Datwyler <redacted>
---
 drivers/of/dynamic.c      | 30 ++++++---------
 include/trace/events/of.h | 93 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 105 insertions(+), 18 deletions(-)
 create mode 100644 include/trace/events/of.h

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index 888fdbc..85c0966 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c

@@ -16,6 +16,9 @@

 #include "of_private.h"

+#define CREATE_TRACE_POINTS
+#include <trace/events/of.h>
+
 /**
  * of_node_get() - Increment refcount of a node
  * @node:      Node to inc refcount, NULL is supported to simplify writing of

@@ -25,8 +28,10 @@
  */
 struct device_node *of_node_get(struct device_node *node)
 {
-       if (node)
+       if (node) {
                kobject_get(&node->kobj);
+               trace_of_node_get(refcount_read(&node->kobj.kref.refcount), node->full_name);

+       }
        return node;
 }
 EXPORT_SYMBOL(of_node_get);

@@ -38,8 +43,10 @@ struct device_node *of_node_get(struct device_node *node)
  */
 void of_node_put(struct device_node *node)
 {
-       if (node)
+       if (node) {
+               trace_of_node_put(refcount_read(&node->kobj.kref.refcount) - 1, node->full_name);
                kobject_put(&node->kobj);
+       }
 }
 EXPORT_SYMBOL(of_node_put);

@@ -92,24 +99,9 @@ int of_reconfig_notifier_unregister(struct notifier_block *nb)
 int of_reconfig_notify(unsigned long action, struct of_reconfig_data *p)
 {
        int rc;
-#ifdef DEBUG
-       struct of_reconfig_data *pr = p;

-       switch (action) {
-       case OF_RECONFIG_ATTACH_NODE:
-       case OF_RECONFIG_DETACH_NODE:
-               pr_debug("notify %-15s %s\n", action_names[action],
-                       pr->dn->full_name);
-               break;
-       case OF_RECONFIG_ADD_PROPERTY:
-       case OF_RECONFIG_REMOVE_PROPERTY:
-       case OF_RECONFIG_UPDATE_PROPERTY:
-               pr_debug("notify %-15s %s:%s\n", action_names[action],
-                       pr->dn->full_name, pr->prop->name);
-               break;
+       trace_of_reconfig_notify(action, p);

-       }
-#endif
        rc = blocking_notifier_call_chain(&of_reconfig_chain, action, p);
        return notifier_to_errno(rc);
 }

@@ -326,6 +318,8 @@ void of_node_release(struct kobject *kobj)
        struct device_node *node = kobj_to_device_node(kobj);
        struct property *prop = node->properties;

+       trace_of_node_release(node);
+
        /* We should never be releasing nodes that haven't been detached. */
        if (!of_node_check_flag(node, OF_DETACHED)) {
                pr_err("ERROR: Bad of_node_put() on %s\n", node->full_name);

diff --git a/include/trace/events/of.h b/include/trace/events/of.h
new file mode 100644
index 0000000..0d53271
--- /dev/null
+++ b/include/trace/events/of.h

@@ -0,0 +1,93 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM of
+
+#if !defined(_TRACE_OF_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_OF_H
+
+#include <linux/of.h>
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(of_node_ref_template,
+
+       TP_PROTO(int refcount, const char* dn_name),
+
+       TP_ARGS(refcount, dn_name),
+
+       TP_STRUCT__entry(
+               __string(dn_name, dn_name)
+               __field(int, refcount)
+       ),
+
+       TP_fast_assign(
+               __assign_str(dn_name, dn_name);
+               __entry->refcount = refcount;
+       ),
+
+       TP_printk("refcount=%d, dn->full_name=%s",
+                 __entry->refcount, __get_str(dn_name))
+);
+
+DEFINE_EVENT(of_node_ref_template, of_node_get,
+            TP_PROTO(int refcount, const char* dn_name),
+            TP_ARGS(refcount, dn_name));
+
+DEFINE_EVENT(of_node_ref_template, of_node_put,
+            TP_PROTO(int refcount, const char* dn_name),
+            TP_ARGS(refcount, dn_name));
+
+TRACE_EVENT(of_node_release,
+
+       TP_PROTO(struct device_node *dn),
+
+       TP_ARGS(dn),
+
+       TP_STRUCT__entry(
+               __string(dn_name, dn->full_name)
+               __field(unsigned long, flags)
+       ),
+
+       TP_fast_assign(
+               __assign_str(dn_name, dn->full_name);
+               __entry->flags = dn->_flags;
+       ),
+
+       TP_printk("dn->full_name=%s, dn->_flags=%lu",
+                 __get_str(dn_name), __entry->flags)
+);
+
+#define of_reconfig_action_names \
+       {OF_RECONFIG_ATTACH_NODE, "ATTACH_NODE"}, \
+       {OF_RECONFIG_DETACH_NODE, "DETACH_NODE"}, \
+       {OF_RECONFIG_ADD_PROPERTY, "ADD_PROPERTY"}, \
+       {OF_RECONFIG_REMOVE_PROPERTY, "REMOVE_PROPERTY"}, \
+       {OF_RECONFIG_UPDATE_PROPERTY, "UPDATE_PROPERTY"}
+
+TRACE_EVENT(of_reconfig_notify,
+
+       TP_PROTO(unsigned long action, struct of_reconfig_data *ord),
+
+       TP_ARGS(action, ord),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, action)
+               __string(dn_name, ord->dn->full_name)
+               __string(prop_name, ord->prop ? ord->prop->name : "null")
+               __string(oldprop_name, ord->old_prop ? ord->old_prop->name : "null")
+       ),
+
+       TP_fast_assign(
+               __entry->action = action;
+               __assign_str(dn_name, ord->dn->full_name);
+               __assign_str(prop_name, ord->prop ? ord->prop->name : "null");
+               __assign_str(oldprop_name, ord->old_prop ? ord->old_prop->name : "null");
+       ),
+
+       TP_printk("action=%s, dn->full_name=%s, prop->name=%s, old_prop->name=%s",
+                 __print_symbolic(__entry->action, of_reconfig_action_names),
+                 __get_str(dn_name), __get_str(prop_name), __get_str(oldprop_name))
+);
+
+#endif /*      _TRACE_OF_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
--

1.8.3.1