opp: Replace list_kref with a local counter

A kref or refcount isn't the right tool to be used here for counting
number of devices that are sharing the static OPPs created for the OPP
table. For example, we are reinitializing the kref again, after it
reaches a value of 0 and frees the resources, if the static OPPs get
added for the same OPP table structure (as the OPP table structure was
never freed). That is messy and very unclear.

This patch makes parsed_static_opps an unsigned integer and uses it to
count the number of users of the static OPPs. The increment and
decrement to parsed_static_opps is done under opp_table->lock now to
make sure no races are possible if the OPP table is getting added and
removed in parallel (which doesn't happen in practice, but can in
theory).

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 11 insertions, 15 deletions

diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index 1e5fcdee043c..9cd8f0adacae 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -658,17 +658,15 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 	struct dev_pm_opp *opp;
 
 	/* OPP table is already initialized for the device */
+	mutex_lock(&opp_table->lock);
 	if (opp_table->parsed_static_opps) {
-		kref_get(&opp_table->list_kref);
+		opp_table->parsed_static_opps++;
+		mutex_unlock(&opp_table->lock);
 		return 0;
 	}
 
-	/*
-	 * Re-initialize list_kref every time we add static OPPs to the OPP
-	 * table as the reference count may be 0 after the last tie static OPPs
-	 * were removed.
-	 */
-	kref_init(&opp_table->list_kref);
+	opp_table->parsed_static_opps = 1;
+	mutex_unlock(&opp_table->lock);
 
 	/* We have opp-table node now, iterate over it and add OPPs */
 	for_each_available_child_of_node(opp_table->np, np) {
@@ -678,7 +676,7 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 			dev_err(dev, "%s: Failed to add OPP, %d\n", __func__,
 				ret);
 			of_node_put(np);
-			goto put_list_kref;
+			goto remove_static_opp;
 		} else if (opp) {
 			count++;
 		}
@@ -687,7 +685,7 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 	/* There should be one of more OPP defined */
 	if (WARN_ON(!count)) {
 		ret = -ENOENT;
-		goto put_list_kref;
+		goto remove_static_opp;
 	}
 
 	list_for_each_entry(opp, &opp_table->opp_list, node)
@@ -698,18 +696,16 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 		dev_err(dev, "Not all nodes have performance state set (%d: %d)\n",
 			count, pstate_count);
 		ret = -ENOENT;
-		goto put_list_kref;
+		goto remove_static_opp;
 	}
 
 	if (pstate_count)
 		opp_table->genpd_performance_state = true;
 
-	opp_table->parsed_static_opps = true;
-
 	return 0;
 
-put_list_kref:
-	_put_opp_list_kref(opp_table);
+remove_static_opp:
+	_opp_remove_all_static(opp_table);
 
 	return ret;
 }
@@ -746,7 +742,7 @@ static int _of_add_opp_table_v1(struct device *dev, struct opp_table *opp_table)
 		if (ret) {
 			dev_err(dev, "%s: Failed to add OPP %ld (%d)\n",
 				__func__, freq, ret);
-			_put_opp_list_kref(opp_table);
+			_opp_remove_all_static(opp_table);
 			return ret;
 		}
 		nr -= 2;