PM / OPP: Fix shared OPP table support in dev_pm_opp_set_supported_hw()

It should be fine to call dev_pm_opp_set_supported_hw() for all possible
CPUs, even if some of them share the OPP table as the caller may not be
aware of sharing policy.

Lets increment the reference count of the OPP table and return its
pointer. The caller need to call dev_pm_opp_put_supported_hw() the same
number of times later on to drop all the references.

To avoid adding another counter to count how many times
dev_pm_opp_set_supported_hw() is called for the same OPP table,
dev_pm_opp_put_supported_hw() frees the resources on the very first call
made to it, assuming that the caller would be calling it sequentially
for all the CPUs. We can revisit that if that assumption is broken in
the future.

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

drivers/opp/core.c

@@ -1157,7 +1157,6 @@ struct opp_table *dev_pm_opp_set_supported_hw(struct device *dev,
 			const u32 *versions, unsigned int count)
 {
 	struct opp_table *opp_table;
-	int ret;
 
 	opp_table = dev_pm_opp_get_opp_table(dev);
 	if (!opp_table)
@@ -1166,29 +1165,20 @@ struct opp_table *dev_pm_opp_set_supported_hw(struct device *dev,
 	/* Make sure there are no concurrent readers while updating opp_table */
 	WARN_ON(!list_empty(&opp_table->opp_list));
 
-	/* Do we already have a version hierarchy associated with opp_table? */
-	if (opp_table->supported_hw) {
-		dev_err(dev, "%s: Already have supported hardware list\n",
-			__func__);
-		ret = -EBUSY;
-		goto err;
-	}
+	/* Another CPU that shares the OPP table has set the property ? */
+	if (opp_table->supported_hw)
+		return opp_table;
 
 	opp_table->supported_hw = kmemdup(versions, count * sizeof(*versions),
 					GFP_KERNEL);
 	if (!opp_table->supported_hw) {
-		ret = -ENOMEM;
-		goto err;
+		dev_pm_opp_put_opp_table(opp_table);
+		return ERR_PTR(-ENOMEM);
 	}
 
 	opp_table->supported_hw_count = count;
 
 	return opp_table;
-
-err:
-	dev_pm_opp_put_opp_table(opp_table);
-
-	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_set_supported_hw);
 
@@ -1205,12 +1195,6 @@ void dev_pm_opp_put_supported_hw(struct opp_table *opp_table)
 	/* Make sure there are no concurrent readers while updating opp_table */
 	WARN_ON(!list_empty(&opp_table->opp_list));
 
-	if (!opp_table->supported_hw) {
-		pr_err("%s: Doesn't have supported hardware list\n",
-		       __func__);
-		return;
-	}
-
 	kfree(opp_table->supported_hw);
 	opp_table->supported_hw = NULL;
 	opp_table->supported_hw_count = 0;