thermal/debugfs: Add debugfs information

The thermal framework does not have any debug information except a
sysfs stat which is a bit controversial. This one allocates big chunks
of memory for every cooling devices with a high number of states and
could represent on some systems in production several megabytes of
memory for just a portion of it. As the syfs is limited to a page
size, the output is not exploitable with large data array and gets
truncated.

The patch provides the same information than sysfs except the
transitions are dynamically allocated, thus they won't represent more
events than the ones which actually occured. There is no longer a size
limitation and it opens the field for more debugging information where
the debugfs is designed for, not sysfs.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/thermal/Kconfig

@@ -33,6 +33,13 @@ config THERMAL_STATISTICS
 
 	  If in doubt, say N.
 
+config THERMAL_DEBUGFS
+	bool "Thermal debugging file system"
+	depends on DEBUG_FS
+	help
+	  This option provides a debugfs entry giving useful
+	  information about the thermal framework internals.
+
 config THERMAL_EMERGENCY_POWEROFF_DELAY_MS
 	int "Emergency poweroff delay in milli-seconds"
 	default 0

drivers/thermal/Makefile

@@ -10,6 +10,9 @@ thermal_sys-y			+= thermal_core.o thermal_sysfs.o \
 # netlink interface to manage the thermal framework
 thermal_sys-$(CONFIG_THERMAL_NETLINK)		+= thermal_netlink.o
 
+# debugfs interface to investigate the behavior and statistics
+thermal_sys-$(CONFIG_THERMAL_DEBUGFS)	+= thermal_debugfs.o
+
 # interface to/from other layers providing sensors
 thermal_sys-$(CONFIG_THERMAL_HWMON)		+= thermal_hwmon.o
 thermal_sys-$(CONFIG_THERMAL_OF)		+= thermal_of.o

drivers/thermal/thermal_core.c

@@ -944,6 +944,8 @@ __thermal_cooling_device_register(struct device_node *np,
 						   THERMAL_EVENT_UNSPECIFIED);
 	mutex_unlock(&thermal_list_lock);
 
+	thermal_debugfs_cdev_register(cdev);
+
 	return cdev;
 
 out_kfree_type:
@@ -1079,6 +1081,8 @@ void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
 	if (!cdev)
 		return;
 
+	thermal_debugfs_cdev_unregister(cdev);
+
 	mutex_lock(&thermal_list_lock);
 	list_for_each_entry(pos, &thermal_cdev_list, node)
 		if (pos == cdev)
@@ -1311,6 +1315,8 @@ thermal_zone_device_register(const char *type, int trips, int mask,
 
 	thermal_notify_tz_create(tz->id, tz->type);
 
+	thermal_debugfs_tz_register(tz);
+
 	return tz;
 
 unregister:
@@ -1340,6 +1346,8 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 	if (!tz)
 		return;
 
+	thermal_debugfs_tz_unregister(tz);
+
 	tzp = tz->tzp;
 	tz_id = tz->id;
 
@@ -1485,6 +1493,8 @@ static int __init thermal_init(void)
 		pr_warn("Thermal: Can not register suspend notifier, return %d\n",
 			result);
 
+	thermal_debugfs_init();
+
 	return 0;
 
 unregister_class:

drivers/thermal/thermal_core.h

@@ -13,6 +13,7 @@
 #include <linux/thermal.h>
 
 #include "thermal_netlink.h"
+#include "thermal_debugfs.h"
 
 /* Default Thermal Governor */
 #if defined(CONFIG_THERMAL_DEFAULT_GOV_STEP_WISE)