thermal: Add devfreq cooling

Add a generic thermal cooling device for devfreq, that is similar to
cpu_cooling.

The device must use devfreq.  In order to use the power extension of the
cooling device, it must have registered its OPPs using the OPP library.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Ørjan Eide <orjan.eide@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/Kconfig

@@ -147,6 +147,20 @@ config CLOCK_THERMAL
 	  device that is configured to use this cooling mechanism will be
 	  controlled to reduce clock frequency whenever temperature is high.
 
+config DEVFREQ_THERMAL
+	bool "Generic device cooling support"
+	depends on PM_DEVFREQ
+	depends on PM_OPP
+	help
+	  This implements the generic devfreq cooling mechanism through
+	  frequency reduction for devices using devfreq.
+
+	  This will throttle the device by limiting the maximum allowed DVFS
+	  frequency corresponding to the cooling level.
+
+	  In order to use the power extensions of the cooling device,
+	  devfreq should use the simple_ondemand governor.
+
 	  If you want this support, you should say Y here.
 
 config THERMAL_EMULATION

drivers/thermal/Makefile

@@ -22,6 +22,9 @@ thermal_sys-$(CONFIG_CPU_THERMAL)	+= cpu_cooling.o
 # clock cooling
 thermal_sys-$(CONFIG_CLOCK_THERMAL)	+= clock_cooling.o
 
+# devfreq cooling
+thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
+
 # platform thermal drivers
 obj-$(CONFIG_QCOM_SPMI_TEMP_ALARM)	+= qcom-spmi-temp-alarm.o
 obj-$(CONFIG_SPEAR_THERMAL)	+= spear_thermal.o

include/linux/devfreq_cooling.h

@@ -0,0 +1,81 @@
+/*
+ * devfreq_cooling: Thermal cooling device implementation for devices using
+ *                  devfreq
+ *
+ * Copyright (C) 2014-2015 ARM Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __DEVFREQ_COOLING_H__
+#define __DEVFREQ_COOLING_H__
+
+#include <linux/devfreq.h>
+#include <linux/thermal.h>
+
+#ifdef CONFIG_DEVFREQ_THERMAL
+
+/**
+ * struct devfreq_cooling_power - Devfreq cooling power ops
+ * @get_static_power:	Take voltage, in mV, and return the static power
+ *			in mW.  If NULL, the static power is assumed
+ *			to be 0.
+ * @get_dynamic_power:	Take voltage, in mV, and frequency, in HZ, and
+ *			return the dynamic power draw in mW.  If NULL,
+ *			a simple power model is used.
+ * @dyn_power_coeff:	Coefficient for the simple dynamic power model in
+ *			mW/(MHz mV mV).
+ *			If get_dynamic_power() is NULL, then the
+ *			dynamic power is calculated as
+ *			@dyn_power_coeff * frequency * voltage^2
+ */
+struct devfreq_cooling_power {
+	unsigned long (*get_static_power)(unsigned long voltage);
+	unsigned long (*get_dynamic_power)(unsigned long freq,
+					   unsigned long voltage);
+	unsigned long dyn_power_coeff;
+};
+
+struct devfreq_cooling_device *
+of_devfreq_cooling_register_power(struct device_node *np, struct devfreq *df,
+				  struct devfreq_cooling_power *dfc_power);
+struct devfreq_cooling_device *
+of_devfreq_cooling_register(struct device_node *np, struct devfreq *df);
+struct devfreq_cooling_device *devfreq_cooling_register(struct devfreq *df);
+void devfreq_cooling_unregister(struct devfreq_cooling_device *dfc);
+
+#else /* !CONFIG_DEVFREQ_THERMAL */
+
+struct devfreq_cooling_device *
+of_devfreq_cooling_register_power(struct device_node *np, struct devfreq *df,
+				  struct devfreq_cooling_power *dfc_power)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+static inline struct devfreq_cooling_device *
+of_devfreq_cooling_register(struct device_node *np, struct devfreq *df)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+static inline struct devfreq_cooling_device *
+devfreq_cooling_register(struct devfreq *df)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+static inline void
+devfreq_cooling_unregister(struct devfreq_cooling_device *dfc)
+{
+}
+
+#endif /* CONFIG_DEVFREQ_THERMAL */
+#endif /* __DEVFREQ_COOLING_H__ */