cpufreq: imx6q: call CPUFREQ_POSTCHANGE notfier in error cases

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.

This also moves PRECHANGE notifier down so that we call it just before starting
frequency transition.

Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/imx6q-cpufreq.c

@@ -68,8 +68,6 @@ static int imx6q_set_target(struct cpufreq_policy *policy,
 	if (freqs.old == freqs.new)
 		return 0;
 
-	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
-
 	rcu_read_lock();
 	opp = opp_find_freq_ceil(cpu_dev, &freq_hz);
 	if (IS_ERR(opp)) {
@@ -86,13 +84,16 @@ static int imx6q_set_target(struct cpufreq_policy *policy,
 		freqs.old / 1000, volt_old / 1000,
 		freqs.new / 1000, volt / 1000);
 
+	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
+
 	/* scaling up?  scale voltage before frequency */
 	if (freqs.new > freqs.old) {
 		ret = regulator_set_voltage_tol(arm_reg, volt, 0);
 		if (ret) {
 			dev_err(cpu_dev,
 				"failed to scale vddarm up: %d\n", ret);
-			return ret;
+			freqs.new = freqs.old;
+			goto post_notify;
 		}
 
 		/*
@@ -145,15 +146,18 @@ static int imx6q_set_target(struct cpufreq_policy *policy,
 	if (ret) {
 		dev_err(cpu_dev, "failed to set clock rate: %d\n", ret);
 		regulator_set_voltage_tol(arm_reg, volt_old, 0);
-		return ret;
+		freqs.new = freqs.old;
+		goto post_notify;
 	}
 
 	/* scaling down?  scale voltage after frequency */
 	if (freqs.new < freqs.old) {
 		ret = regulator_set_voltage_tol(arm_reg, volt, 0);
-		if (ret)
+		if (ret) {
 			dev_warn(cpu_dev,
 				 "failed to scale vddarm down: %d\n", ret);
+			ret = 0;
+		}
 
 		if (freqs.old == FREQ_1P2_GHZ / 1000) {
 			regulator_set_voltage_tol(pu_reg,
@@ -163,9 +167,10 @@ static int imx6q_set_target(struct cpufreq_policy *policy,
 		}
 	}
 
+post_notify:
 	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
 
-	return 0;
+	return ret;
 }
 
 static int imx6q_cpufreq_init(struct cpufreq_policy *policy)