thermal: intel: powerclamp: Fix duration module parameter

After the switch to use the powercap/idle-inject framework in the Intel
powerclamp driver, the idle duration unit is microsecond.

However, the module parameter for idle duration is in milliseconds, so
convert it to microseconds in the "set" callback and back to milliseconds
in a new "get" callback.

While here, also use mutex protection for setting and getting "duration".

The other uses of "duration" are already protected by the mutex.

Fixes: 8526eb7f ("thermal: intel: powerclamp: Use powercap idle-inject feature")
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/thermal/intel/intel_powerclamp.c

@@ -74,6 +74,7 @@ static struct thermal_cooling_device *cooling_dev;
 
 static DEFINE_MUTEX(powerclamp_lock);
 
+/* This duration is in microseconds */
 static unsigned int duration;
 static unsigned int pkg_cstate_ratio_cur;
 static unsigned int window_size;
@@ -90,23 +91,34 @@ static int duration_set(const char *arg, const struct kernel_param *kp)
 		pr_err("Out of recommended range %lu, between 6-25ms\n",
 			new_duration);
 		ret = -EINVAL;
+		goto exit;
 	}
 
-	duration = clamp(new_duration, 6ul, 25ul);
-	smp_mb();
-
+	mutex_lock(&powerclamp_lock);
+	duration = clamp(new_duration, 6ul, 25ul) * 1000;
+	mutex_unlock(&powerclamp_lock);
 exit:
 
 	return ret;
 }
 
+static int duration_get(char *buf, const struct kernel_param *kp)
+{
+	int ret;
+
+	mutex_lock(&powerclamp_lock);
+	ret = sysfs_emit(buf, "%d\n", duration / 1000);
+	mutex_unlock(&powerclamp_lock);
+
+	return ret;
+}
+
 static const struct kernel_param_ops duration_ops = {
 	.set = duration_set,
-	.get = param_get_int,
+	.get = duration_get,
 };
 
-
-module_param_cb(duration, &duration_ops, &duration, 0644);
+module_param_cb(duration, &duration_ops, NULL, 0644);
 MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec.");
 
 struct powerclamp_calibration_data {