devfreq: rk3399_dmc: Don't use OPP structures outside of RCU locks

The OPP structures are abused to the best here, without understanding
how the OPP core and RCU locks work.

In short, the OPP pointer saved in 'rk3399_dmcfreq' can become invalid
under your nose, as the OPP core may free it.

Fix various abuses around OPP structures and calls.
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/devfreq/rk3399_dmc.c

@@ -80,7 +80,6 @@ struct rk3399_dmcfreq {
 	struct regulator *vdd_center;
 	unsigned long rate, target_rate;
 	unsigned long volt, target_volt;
-	struct dev_pm_opp *curr_opp;
 };
 
 static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
@@ -102,9 +101,6 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
 	target_rate = dev_pm_opp_get_freq(opp);
 	target_volt = dev_pm_opp_get_voltage(opp);
 
-	dmcfreq->rate = dev_pm_opp_get_freq(dmcfreq->curr_opp);
-	dmcfreq->volt = dev_pm_opp_get_voltage(dmcfreq->curr_opp);
-
 	rcu_read_unlock();
 
 	if (dmcfreq->rate == target_rate)
@@ -165,7 +161,9 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
 	if (err)
 		dev_err(dev, "Cannot to set vol %lu uV\n", target_volt);
 
-	dmcfreq->curr_opp = opp;
+	dmcfreq->rate = target_rate;
+	dmcfreq->volt = target_volt;
+
 out:
 	mutex_unlock(&dmcfreq->lock);
 	return err;
@@ -430,8 +428,9 @@ static int rk3399_dmcfreq_probe(struct platform_device *pdev)
 		rcu_read_unlock();
 		return PTR_ERR(opp);
 	}
+	data->rate = dev_pm_opp_get_freq(opp);
+	data->volt = dev_pm_opp_get_voltage(opp);
 	rcu_read_unlock();
-	data->curr_opp = opp;
 
 	rk3399_devfreq_dmc_profile.initial_freq = data->rate;