thermal: cpu_cooling: Fix NULL dereference in cpufreq_state2power

Currently all CPU cooling devices share a
`struct thermal_cooling_device_ops` instance. The thermal core uses the
presence of functions in this struct to determine if a cooling device
has a power model (see cdev_is_power_actor). cpu_cooling.c adds the
power model functions to the shared struct when a device is registered
with a power model.

Therefore, if a CPU cooling device is registered using
[of_]cpufreq_power_cooling_register, _all_ devices will be determined to
have a power model, including any registered with
[of_]cpufreq_cooling_register. This can result in cpufreq_state2power
being called on a device where dyn_power_table is NULL.

With this commit, instead of having a shared thermal_cooling_device_ops
which is mutated, we have two versions: one with the power functions and
one without.

Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@gmail.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Javi Merino <javi.merino@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/cpu_cooling.c

@@ -740,12 +740,22 @@ static int cpufreq_power2state(struct thermal_cooling_device *cdev,
 }
 
 /* Bind cpufreq callbacks to thermal cooling device ops */
+
 static struct thermal_cooling_device_ops cpufreq_cooling_ops = {
 	.get_max_state = cpufreq_get_max_state,
 	.get_cur_state = cpufreq_get_cur_state,
 	.set_cur_state = cpufreq_set_cur_state,
 };
 
+static struct thermal_cooling_device_ops cpufreq_power_cooling_ops = {
+	.get_max_state		= cpufreq_get_max_state,
+	.get_cur_state		= cpufreq_get_cur_state,
+	.set_cur_state		= cpufreq_set_cur_state,
+	.get_requested_power	= cpufreq_get_requested_power,
+	.state2power		= cpufreq_state2power,
+	.power2state		= cpufreq_power2state,
+};
+
 /* Notifier for cpufreq policy change */
 static struct notifier_block thermal_cpufreq_notifier_block = {
 	.notifier_call = cpufreq_thermal_notifier,
@@ -795,6 +805,7 @@ __cpufreq_cooling_register(struct device_node *np,
 	struct cpumask temp_mask;
 	unsigned int freq, i, num_cpus;
 	int ret;
+	struct thermal_cooling_device_ops *cooling_ops;
 
 	cpumask_and(&temp_mask, clip_cpus, cpu_online_mask);
 	policy = cpufreq_cpu_get(cpumask_first(&temp_mask));
@@ -850,10 +861,6 @@ __cpufreq_cooling_register(struct device_node *np,
 	cpumask_copy(&cpufreq_dev->allowed_cpus, clip_cpus);
 
 	if (capacitance) {
-		cpufreq_cooling_ops.get_requested_power =
-			cpufreq_get_requested_power;
-		cpufreq_cooling_ops.state2power = cpufreq_state2power;
-		cpufreq_cooling_ops.power2state = cpufreq_power2state;
 		cpufreq_dev->plat_get_static_power = plat_static_func;
 
 		ret = build_dyn_power_table(cpufreq_dev, capacitance);
@@ -861,6 +868,10 @@ __cpufreq_cooling_register(struct device_node *np,
 			cool_dev = ERR_PTR(ret);
 			goto free_table;
 		}
+
+		cooling_ops = &cpufreq_power_cooling_ops;
+	} else {
+		cooling_ops = &cpufreq_cooling_ops;
 	}
 
 	ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
@@ -885,7 +896,7 @@ __cpufreq_cooling_register(struct device_node *np,
 		 cpufreq_dev->id);
 
 	cool_dev = thermal_of_cooling_device_register(np, dev_name, cpufreq_dev,
-						      &cpufreq_cooling_ops);
+						      cooling_ops);
 	if (IS_ERR(cool_dev))
 		goto remove_idr;