thermal: introduce device tree parser

This patch introduces a device tree bindings for
describing the hardware thermal behavior and limits.
Also a parser to read and interpret the data and feed
it in the thermal framework is presented.

This patch introduces a thermal data parser for device
tree. The parsed data is used to build thermal zones
and thermal binding parameters. The output data
can then be used to deploy thermal policies.

This patch adds also documentation regarding this
API and how to define tree nodes to use
this infrastructure.

Note that, in order to be able to have control
on the sensor registration on the DT thermal zone,
it was required to allow changing the thermal zone
.get_temp callback. For this reason, this patch
also removes the 'const' modifier from the .ops
field of thermal zone devices.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>

drivers/thermal/Kconfig

@@ -29,6 +29,19 @@ config THERMAL_HWMON
 	  Say 'Y' here if you want all thermal sensors to
 	  have hwmon sysfs interface too.
 
+config THERMAL_OF
+	bool
+	prompt "APIs to parse thermal data out of device tree"
+	depends on OF
+	default y
+	help
+	  This options provides helpers to add the support to
+	  read and parse thermal data definitions out of the
+	  device tree blob.
+
+	  Say 'Y' here if you need to build thermal infrastructure
+	  based on device tree.
+
 choice
 	prompt "Default Thermal governor"
 	default THERMAL_DEFAULT_GOV_STEP_WISE

drivers/thermal/Makefile

@@ -7,6 +7,7 @@ thermal_sys-y			+= thermal_core.o
 
 # interface to/from other layers providing sensors
 thermal_sys-$(CONFIG_THERMAL_HWMON)		+= thermal_hwmon.o
+thermal_sys-$(CONFIG_THERMAL_OF)		+= of-thermal.o
 
 # governors
 thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE)	+= fair_share.o

drivers/thermal/thermal_core.c

@@ -1373,7 +1373,7 @@ static void remove_trip_attrs(struct thermal_zone_device *tz)
  */
 struct thermal_zone_device *thermal_zone_device_register(const char *type,
 	int trips, int mask, void *devdata,
-	const struct thermal_zone_device_ops *ops,
+	struct thermal_zone_device_ops *ops,
 	const struct thermal_zone_params *tzp,
 	int passive_delay, int polling_delay)
 {
@@ -1746,8 +1746,14 @@ static int __init thermal_init(void)
 	if (result)
 		goto unregister_class;
 
+	result = of_parse_thermal_zones();
+	if (result)
+		goto exit_netlink;
+
 	return 0;
 
+exit_netlink:
+	genetlink_exit();
 unregister_governors:
 	thermal_unregister_governors();
 unregister_class:
@@ -1763,6 +1769,7 @@ static int __init thermal_init(void)
 
 static void __exit thermal_exit(void)
 {
+	of_thermal_destroy_zones();
 	genetlink_exit();
 	class_unregister(&thermal_class);
 	thermal_unregister_governors();

drivers/thermal/thermal_core.h

@@ -77,4 +77,13 @@ static inline int thermal_gov_user_space_register(void) { return 0; }
 static inline void thermal_gov_user_space_unregister(void) {}
 #endif /* CONFIG_THERMAL_GOV_USER_SPACE */
 
+/* device tree support */
+#ifdef CONFIG_THERMAL_OF
+int of_parse_thermal_zones(void);
+void of_thermal_destroy_zones(void);
+#else
+static inline int of_parse_thermal_zones(void) { return 0; }
+static inline void of_thermal_destroy_zones(void) { }
+#endif
+
 #endif /* __THERMAL_CORE_H__ */

include/dt-bindings/thermal/thermal.h

+/*
+ * This header provides constants for most thermal bindings.
+ *
+ * Copyright (C) 2013 Texas Instruments
+ *	Eduardo Valentin <eduardo.valentin@ti.com>
+ *
+ * GPLv2 only
+ */
+
+#ifndef _DT_BINDINGS_THERMAL_THERMAL_H
+#define _DT_BINDINGS_THERMAL_THERMAL_H
+
+/* On cooling devices upper and lower limits */
+#define THERMAL_NO_LIMIT		(-1UL)
+
+#endif
+

include/linux/thermal.h

@@ -143,6 +143,7 @@ struct thermal_cooling_device {
 	int id;
 	char type[THERMAL_NAME_LENGTH];
 	struct device device;
+	struct device_node *np;
 	void *devdata;
 	const struct thermal_cooling_device_ops *ops;
 	bool updated; /* true if the cooling device does not need update */
@@ -172,7 +173,7 @@ struct thermal_zone_device {
 	int emul_temperature;
 	int passive;
 	unsigned int forced_passive;
-	const struct thermal_zone_device_ops *ops;
+	struct thermal_zone_device_ops *ops;
 	const struct thermal_zone_params *tzp;
 	struct thermal_governor *governor;
 	struct list_head thermal_instances;
@@ -242,8 +243,31 @@ struct thermal_genl_event {
 };
 
 /* Function declarations */
+#ifdef CONFIG_THERMAL_OF
+struct thermal_zone_device *
+thermal_zone_of_sensor_register(struct device *dev, int id,
+				void *data, int (*get_temp)(void *, long *),
+				int (*get_trend)(void *, long *));
+void thermal_zone_of_sensor_unregister(struct device *dev,
+				       struct thermal_zone_device *tz);
+#else
+static inline struct thermal_zone_device *
+thermal_zone_of_sensor_register(struct device *dev, int id,
+				void *data, int (*get_temp)(void *, long *),
+				int (*get_trend)(void *, long *))
+{
+	return NULL;
+}
+
+static inline
+void thermal_zone_of_sensor_unregister(struct device *dev,
+				       struct thermal_zone_device *tz)
+{
+}
+
+#endif
 struct thermal_zone_device *thermal_zone_device_register(const char *, int, int,
-		void *, const struct thermal_zone_device_ops *,
+		void *, struct thermal_zone_device_ops *,
 		const struct thermal_zone_params *, int, int);
 void thermal_zone_device_unregister(struct thermal_zone_device *);