PM / OPP: Update OPP users to put reference

This patch updates dev_pm_opp_find_freq_*() routines to get a reference
to the OPPs returned by them.

Also updates the users of dev_pm_opp_find_freq_*() routines to call
dev_pm_opp_put() after they are done using the OPPs.

As it is guaranteed the that OPPs wouldn't get freed while being used,
the RCU read side locking present with the users isn't required anymore.
Drop it as well.

This patch also updates all users of devfreq_recommended_opp() which was
returning an OPP received from the OPP core.

Note that some of the OPP core routines have gained
rcu_read_{lock|unlock}() calls, as those still use RCU specific APIs
within them.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> [Devfreq]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 4 insertions, 10 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a545c0fee6e1..253525ea17af 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -111,18 +111,16 @@ static void devfreq_set_freq_table(struct devfreq *devfreq)
                 return;
         }
 
-        rcu_read_lock();
         for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
                 opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
                 if (IS_ERR(opp)) {
                         devm_kfree(devfreq->dev.parent, profile->freq_table);
                         profile->max_state = 0;
-                        rcu_read_unlock();
                         return;
                 }
+                dev_pm_opp_put(opp);
                 profile->freq_table[i] = freq;
         }
-        rcu_read_unlock();
 }
 
 /**
@@ -1112,17 +1110,16 @@ static ssize_t available_frequencies_show(struct device *d,
         ssize_t count = 0;
         unsigned long freq = 0;
 
-        rcu_read_lock();
         do {
                 opp = dev_pm_opp_find_freq_ceil(dev, &freq);
                 if (IS_ERR(opp))
                         break;
 
+                dev_pm_opp_put(opp);
                 count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
                                    "%lu ", freq);
                 freq++;
         } while (1);
-        rcu_read_unlock();
 
         /* Truncate the trailing space */
         if (count)
@@ -1224,11 +1221,8 @@ subsys_initcall(devfreq_init);
  * @freq:       The frequency given to target function
  * @flags:      Flags handed from devfreq framework.
  *
- * Locking: This function must be called under rcu_read_lock(). opp is a rcu
- * protected pointer. The reason for the same is that the opp pointer which is
- * returned will remain valid for use with opp_get_{voltage, freq} only while
- * under the locked area. The pointer returned must be used prior to unlocking
- * with rcu_read_unlock() to maintain the integrity of the pointer.
+ * The callers are required to call dev_pm_opp_put() for the returned OPP after
+ * use.
  */
 struct dev_pm_opp *devfreq_recommended_opp(struct device *dev,
                                            unsigned long *freq,