cpufreq: Auto-register the driver as a thermal cooling device if asked

All cpufreq drivers do similar things to register as a cooling device.
Provide a cpufreq driver flag so drivers can just ask the cpufreq core
to register the cooling device on their behalf. This allows us to get
rid of duplicated code in the drivers.

In order to allow this, we add a struct thermal_cooling_device pointer
to struct cpufreq_policy so that drivers don't need to store it in a
private data structure.

Suggested-by: Stephen Boyd <swboyd@chromium.org>
Suggested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -19,6 +19,7 @@
 
 #include <linux/cpu.h>
 #include <linux/cpufreq.h>
+#include <linux/cpu_cooling.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/init.h>
@@ -1316,6 +1317,10 @@ static int cpufreq_online(unsigned int cpu)
 	if (cpufreq_driver->ready)
 		cpufreq_driver->ready(policy);
 
+	if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
+	    cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV)
+		policy->cdev = of_cpufreq_cooling_register(policy);
+
 	pr_debug("initialization complete\n");
 
 	return 0;
@@ -1403,6 +1408,12 @@ static int cpufreq_offline(unsigned int cpu)
 		goto unlock;
 	}
 
+	if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
+	    cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV) {
+		cpufreq_cooling_unregister(policy->cdev);
+		policy->cdev = NULL;
+	}
+
 	if (cpufreq_driver->stop_cpu)
 		cpufreq_driver->stop_cpu(policy);
 

include/linux/cpufreq.h

@@ -151,6 +151,9 @@ struct cpufreq_policy {
 
 	/* For cpufreq driver's internal use */
 	void			*driver_data;
+
+	/* Pointer to the cooling device if used for thermal mitigation */
+	struct thermal_cooling_device *cdev;
 };
 
 /* Only for ACPI */
@@ -378,6 +381,12 @@ struct cpufreq_driver {
  */
 #define CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING	BIT(6)
 
+/*
+ * Set by drivers that want the core to automatically register the cpufreq
+ * driver as a thermal cooling device.
+ */
+#define CPUFREQ_IS_COOLING_DEV			BIT(7)
+
 int cpufreq_register_driver(struct cpufreq_driver *driver_data);
 int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);