[v6,1/2] thermal/debugfs: Add thermal cooling device debugfs information

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index c81a00fbca7d..3ff7add3fb7c 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -33,6 +33,13 @@  config THERMAL_STATISTICS
 
 	  If in doubt, say N.
 
+config THERMAL_DEBUGFS
+	bool "Thermal subsystem debug support"
+	depends on DEBUG_FS
+	help
+	  Say Y to allow the thermal subsystem to collect diagnostic
+	  information that can be accessed via debugfs.
+
 config THERMAL_EMERGENCY_POWEROFF_DELAY_MS
 	int "Emergency poweroff delay in milli-seconds"
 	default 0
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index c934cab309ae..0f65ae86a9c6 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -10,6 +10,8 @@  thermal_sys-y			+= thermal_trip.o thermal_helpers.o
 # netlink interface to manage the thermal framework
 thermal_sys-$(CONFIG_THERMAL_NETLINK)		+= thermal_netlink.o
 
+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
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 625ba07cbe2f..33332d401b13 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -945,6 +945,8 @@  __thermal_cooling_device_register(struct device_node *np,
 
 	mutex_unlock(&thermal_list_lock);
 
+	thermal_debug_cdev_add(cdev);
+	
 	return cdev;
 
 out_cooling_dev:
@@ -1151,6 +1153,8 @@  void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
 	if (!cdev)
 		return;
 
+	thermal_debug_cdev_remove(cdev);
+
 	mutex_lock(&thermal_list_lock);
 
 	if (!thermal_cooling_device_present(cdev)) {
@@ -1570,6 +1574,8 @@  static int __init thermal_init(void)
 {
 	int result;
 
+	thermal_debug_init();
+
 	result = thermal_netlink_init();
 	if (result)
 		goto error;
diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index 7dfe6c8deb8e..4b3452a65a2f 100644
--- a/drivers/thermal/thermal_core.h
+++ b/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)
diff --git a/drivers/thermal/thermal_debugfs.c b/drivers/thermal/thermal_debugfs.c
new file mode 100644
index 000000000000..84e5ef3dc16c
--- /dev/null
+++ b/drivers/thermal/thermal_debugfs.c
@@ -0,0 +1,445 @@ 
+
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2023 Linaro Limited
+ *
+ * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
+ *
+ * Thermal subsystem debug support
+ */
+#include <linux/debugfs.h>
+#include <linux/ktime.h>
+#include <linux/list.h>
+#include <linux/minmax.h>
+#include <linux/mutex.h>
+#include <linux/thermal.h>
+
+static struct dentry *d_root;
+static struct dentry *d_cdev;
+
+/*
+ * Length of the string containing the thermal zone id or the cooling
+ * device id, including the ending nul character. We can reasonably
+ * assume there won't be more than 256 thermal zones as the maximum
+ * observed today is around 32.
+ */
+#define IDSLENGTH 4
+
+/*
+ * The cooling device transition list is stored in a hash table where
+ * the size is CDEVSTATS_HASH_SIZE. The majority of cooling devices
+ * have dozen of states but some can have much more, so a hash table
+ * is more adequate in this case, because the cost of browsing the entire
+ * list when storing the transitions may not be negligible.
+ */
+#define CDEVSTATS_HASH_SIZE 16
+
+/**
+ * struct cdev_debugfs - per cooling device statistics structure
+ * A cooling device can have a high number of states. Showing the
+ * transitions on a matrix based representation can be overkill given
+ * most of the transitions won't happen and we end up with a matrix
+ * filled with zero. Instead, we show the transitions which actually
+ * happened.
+ *
+ * Every transition updates the current_state and the timestamp. The
+ * transitions and the durations are stored in lists.
+ *
+ * @total: the number of transitions for this cooling device
+ * @current_state: the current cooling device state
+ * @timestamp: the state change timestamp
+ * @transitions: an array of lists containing the state transitions
+ * @durations: an array of lists containing the residencies of each state
+ */
+struct cdev_debugfs {
+	u32 total;
+	int current_state;
+	ktime_t timestamp;
+	struct list_head transitions[CDEVSTATS_HASH_SIZE];
+	struct list_head durations[CDEVSTATS_HASH_SIZE];
+};
+
+/**
+ * struct cdev_value - Common structure for cooling device entry
+ *
+ * The following common structure allows to store the information
+ * related to the transitions and to the state residencies. They are
+ * identified with a id which is associated to a value. It is used as
+ * nodes for the "transitions" and "durations" above.
+ *
+ * @node: node to insert the structure in a list
+ * @id: identifier of the value which can be a state or a transition
+ * @residency: a ktime_t representing a state residency duration
+ * @count: a number of occurrences
+ */
+struct cdev_record {
+	struct list_head node;
+	int id;
+	union {
+                ktime_t residency;
+                u64 count;
+        };
+};
+
+/**
+ * struct thermal_debugfs - High level structure for a thermal object in debugfs
+ *
+ * The thermal_debugfs structure is the common structure used by the
+ * cooling device to compute the statistics.
+ *
+ * @d_top: top directory of the thermal object directory
+ * @lock: per object lock to protect the internals
+ *
+ * @cdev: a cooling device debug structure
+ */
+struct thermal_debugfs {
+	struct dentry *d_top;
+	struct mutex lock;
+	union {
+		struct cdev_debugfs cdev_dbg;
+	};
+};
+
+void thermal_debug_init(void)
+{
+	d_root = debugfs_create_dir("thermal", NULL);
+	if (!d_root)
+		return;
+
+	d_cdev = debugfs_create_dir("cooling_devices", d_root);
+}
+
+static struct thermal_debugfs *thermal_debugfs_add_id(struct dentry *d, int id)
+{
+	struct thermal_debugfs *thermal_dbg;
+	char ids[IDSLENGTH];
+
+	thermal_dbg = kzalloc(sizeof(*thermal_dbg), GFP_KERNEL);
+	if (!thermal_dbg)
+		return NULL;
+
+	mutex_init(&thermal_dbg->lock);
+	
+	snprintf(ids, IDSLENGTH, "%d", id);
+
+	thermal_dbg->d_top = debugfs_create_dir(ids, d);
+	if (!thermal_dbg->d_top) {
+		kfree(thermal_dbg);
+		return NULL;
+	}
+
+	return thermal_dbg;
+}
+
+static void thermal_debugfs_remove_id(struct thermal_debugfs *thermal_dbg)
+{
+	if (!thermal_dbg)
+		return;
+
+	debugfs_remove(thermal_dbg->d_top);
+
+	kfree(thermal_dbg);
+}
+
+static struct cdev_record *
+thermal_debugfs_cdev_record_alloc(struct thermal_debugfs *thermal_dbg,
+				  struct list_head *lists, int id)
+{
+	struct cdev_record *cdev_record;
+
+	cdev_record = kzalloc(sizeof(*cdev_record), GFP_KERNEL);
+	if (!cdev_record)
+		return NULL;
+
+	cdev_record->id = id;
+	INIT_LIST_HEAD(&cdev_record->node);
+	list_add_tail(&cdev_record->node,
+		      &lists[cdev_record->id % CDEVSTATS_HASH_SIZE]);
+
+	return cdev_record;
+}
+
+static struct cdev_record *
+thermal_debugfs_cdev_record_find(struct thermal_debugfs *thermal_dbg,
+				 struct list_head *lists, int id)
+{
+	struct cdev_record *entry;
+
+	list_for_each_entry(entry, &lists[id % CDEVSTATS_HASH_SIZE], node)
+		if (entry->id == id)
+			return entry;
+
+	return NULL;
+}
+
+static struct cdev_record *
+thermal_debugfs_cdev_record_get(struct thermal_debugfs *thermal_dbg,
+				struct list_head *lists, int id)
+{
+	struct cdev_record *cdev_record;
+
+	cdev_record = thermal_debugfs_cdev_record_find(thermal_dbg, lists, id);
+	if (cdev_record)
+		return cdev_record;
+
+	return thermal_debugfs_cdev_record_alloc(thermal_dbg, lists, id);
+}
+
+static void thermal_debugfs_cdev_clear(struct cdev_debugfs *cdev_dbg)
+{
+	int i;
+	struct cdev_record *entry, *tmp;
+
+	for (i = 0; i < CDEVSTATS_HASH_SIZE; i++) {
+
+		list_for_each_entry_safe(entry, tmp,
+					 &cdev_dbg->transitions[i], node) {
+			list_del(&entry->node);
+			kfree(entry);
+		}
+
+		list_for_each_entry_safe(entry, tmp,
+					 &cdev_dbg->durations[i], node) {
+			list_del(&entry->node);
+			kfree(entry);
+		}
+	}
+
+	cdev_dbg->total = 0;
+}
+
+static void *cdev_seq_start(struct seq_file *s, loff_t *pos)
+{
+	struct thermal_debugfs *thermal_dbg = s->private;
+
+	mutex_lock(&thermal_dbg->lock);
+
+	return (*pos < CDEVSTATS_HASH_SIZE) ? pos : NULL;
+}
+
+static void *cdev_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	(*pos)++;
+
+	return (*pos < CDEVSTATS_HASH_SIZE) ? pos : NULL;
+}
+
+static void cdev_seq_stop(struct seq_file *s, void *v)
+{
+	struct thermal_debugfs *thermal_dbg = s->private;
+
+	mutex_unlock(&thermal_dbg->lock);
+}
+
+static int cdev_tt_seq_show(struct seq_file *s, void *v)
+{
+	struct thermal_debugfs *thermal_dbg = s->private;	
+	struct cdev_debugfs *cdev_dbg = &thermal_dbg->cdev_dbg;
+	struct list_head *transitions = cdev_dbg->transitions;
+	struct cdev_record *entry;
+	int i = *(loff_t *)v;
+
+	if (!i)
+		seq_puts(s, "Transition\tOccurences\n");
+
+	list_for_each_entry(entry, &transitions[i], node) {
+		/*
+		 * Assuming maximum cdev states is 1024, the longer
+		 * string for a transition would be "1024->1024\0"
+		 */
+		char buffer[11];
+		
+		snprintf(buffer, ARRAY_SIZE(buffer), "%d->%d",
+			 entry->id >> 16, entry->id & 0xFFFF);
+
+		seq_printf(s, "%-10s\t%-10llu\n", buffer, entry->count);
+	}
+
+	return 0;
+}
+
+static const struct seq_operations tt_sops = {
+	.start = cdev_seq_start,
+	.next = cdev_seq_next,
+	.stop = cdev_seq_stop,
+	.show = cdev_tt_seq_show,
+};
+
+DEFINE_SEQ_ATTRIBUTE(tt);
+
+static int cdev_dt_seq_show(struct seq_file *s, void *v)
+{
+	struct thermal_debugfs *thermal_dbg = s->private;
+	struct cdev_debugfs *cdev_dbg = &thermal_dbg->cdev_dbg;
+	struct list_head *durations = cdev_dbg->durations;
+	struct cdev_record *entry;
+	int i = *(loff_t *)v;
+
+	if (!i)
+		seq_puts(s, "State\tResidency\n");
+
+	list_for_each_entry(entry, &durations[i], node) {
+		s64 duration = ktime_to_ms(entry->residency);
+
+		if (entry->id == cdev_dbg->current_state)
+			duration += ktime_ms_delta(ktime_get(),
+						   cdev_dbg->timestamp);
+
+		seq_printf(s, "%-5d\t%-10llu\n", entry->id, duration);
+	}
+
+	return 0;
+}
+
+static const struct seq_operations dt_sops = {
+	.start = cdev_seq_start,
+	.next = cdev_seq_next,
+	.stop = cdev_seq_stop,
+	.show = cdev_dt_seq_show,
+};
+
+DEFINE_SEQ_ATTRIBUTE(dt);
+
+static int cdev_clear_set(void *data, u64 val)
+{
+	struct thermal_debugfs *thermal_dbg = data;
+
+	if (!val)
+		return -EINVAL;
+
+	mutex_lock(&thermal_dbg->lock);
+	
+	thermal_debugfs_cdev_clear(&thermal_dbg->cdev_dbg);
+
+	mutex_unlock(&thermal_dbg->lock);
+
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(cdev_clear_fops, NULL, cdev_clear_set, "%llu\n");
+
+/**
+ * thermal_debug_cdev_state_update - Update a cooling device state change
+ *
+ * Computes a transition and the duration of the previous state residency.
+ *
+ * @cdev : a pointer to a cooling device
+ * @new_state: an integer corresponding to the new cooling device state
+ */
+void thermal_debug_cdev_state_update(const struct thermal_cooling_device *cdev,
+				     int new_state)
+{
+	struct thermal_debugfs *thermal_dbg = cdev->debugfs;
+	struct cdev_debugfs *cdev_dbg;
+	struct cdev_record *cdev_record;
+	int transition, old_state;
+
+	if (!thermal_dbg || (thermal_dbg->cdev_dbg.current_state == new_state))
+		return;
+
+	mutex_lock(&thermal_dbg->lock);
+
+	cdev_dbg = &thermal_dbg->cdev_dbg;
+
+	old_state = cdev_dbg->current_state;
+
+	/*
+	 * Get the old state information in the durations list. If
+	 * this one does not exist, a new allocated one will be
+	 * returned. Recompute the total duration in the old state and
+	 * get a new timestamp for the new state.
+	 */
+	cdev_record = thermal_debugfs_cdev_record_get(thermal_dbg,
+						      cdev_dbg->durations,
+						      old_state);
+	if (cdev_record) {
+		ktime_t now = ktime_get();
+		ktime_t delta = ktime_sub(now, cdev_dbg->timestamp);
+		cdev_record->residency = ktime_add(cdev_record->residency, delta);
+		cdev_dbg->timestamp = now;
+	}
+
+	cdev_dbg->current_state = new_state;
+	transition = (old_state << 16) | new_state;
+	
+	/*
+	 * Get the transition in the transitions list. If this one
+	 * does not exist, a new allocated one will be returned.
+	 * Increment the occurrence of this transition which is stored
+	 * in the value field.
+	 */
+	cdev_record = thermal_debugfs_cdev_record_get(thermal_dbg,
+						      cdev_dbg->transitions,
+						      transition);
+	if (cdev_record)
+		cdev_record->count++;
+
+	cdev_dbg->total++;
+
+	mutex_unlock(&thermal_dbg->lock);
+}
+
+/**
+ * thermal_debug_cdev_add - Add a cooling device debugfs entry
+ *
+ * Allocates a cooling device object for debug, initializes the
+ * statistics and create the entries in sysfs.
+ * @cdev: a pointer to a cooling device
+ */
+void thermal_debug_cdev_add(struct thermal_cooling_device *cdev)
+{
+	struct thermal_debugfs *thermal_dbg;
+	struct cdev_debugfs *cdev_dbg;
+	int i;
+
+	thermal_dbg = thermal_debugfs_add_id(d_cdev, cdev->id);
+	if (!thermal_dbg)
+		return;
+
+	cdev_dbg = &thermal_dbg->cdev_dbg;
+
+	for (i = 0; i < CDEVSTATS_HASH_SIZE; i++) {
+		INIT_LIST_HEAD(&cdev_dbg->transitions[i]);
+		INIT_LIST_HEAD(&cdev_dbg->durations[i]);
+	}
+
+	cdev_dbg->current_state = 0;
+	cdev_dbg->timestamp = ktime_get();
+
+	debugfs_create_file("trans_table", 0400, thermal_dbg->d_top,
+			    thermal_dbg, &tt_fops);
+
+	debugfs_create_file("time_in_state_ms", 0400, thermal_dbg->d_top,
+			    thermal_dbg, &dt_fops);
+
+	debugfs_create_file("clear", 0200, thermal_dbg->d_top,
+			    thermal_dbg, &cdev_clear_fops);
+
+	debugfs_create_u32("total_trans", 0400, thermal_dbg->d_top,
+			   &cdev_dbg->total);
+
+	cdev->debugfs = thermal_dbg;
+}
+
+/**
+ * thermal_debug_cdev_remove - Remove a cooling device debugfs entry
+ *
+ * Frees the statistics memory data and remove the debugfs entry
+ *
+ * @cdev: a pointer to a cooling device
+ */
+void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
+{
+	struct thermal_debugfs *thermal_dbg = cdev->debugfs;
+
+	if (!thermal_dbg)
+		return;
+
+	mutex_lock(&thermal_dbg->lock);
+	
+	thermal_debugfs_cdev_clear(&thermal_dbg->cdev_dbg);
+	cdev->debugfs = NULL;
+	thermal_debugfs_remove_id(thermal_dbg);
+
+	mutex_unlock(&thermal_dbg->lock);
+}
diff --git a/drivers/thermal/thermal_debugfs.h b/drivers/thermal/thermal_debugfs.h
new file mode 100644
index 000000000000..341499388448
--- /dev/null
+++ b/drivers/thermal/thermal_debugfs.h
@@ -0,0 +1,14 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifdef CONFIG_THERMAL_DEBUGFS
+void thermal_debug_init(void);
+void thermal_debug_cdev_add(struct thermal_cooling_device *cdev);
+void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev);
+void thermal_debug_cdev_state_update(const struct thermal_cooling_device *cdev, int state);
+#else
+static inline void thermal_debug_init(void) {}
+static inline void thermal_debug_cdev_add(struct thermal_cooling_device *cdev) {}
+static inline void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev) {}
+static inline void thermal_debug_cdev_state_update(const struct thermal_cooling_device *cdev,
+						   int state) {}
+#endif /* CONFIG_THERMAL_DEBUGFS */
diff --git a/drivers/thermal/thermal_helpers.c b/drivers/thermal/thermal_helpers.c
index 69e8ea4aa908..c9e3d6626453 100644
--- a/drivers/thermal/thermal_helpers.c
+++ b/drivers/thermal/thermal_helpers.c
@@ -151,14 +151,22 @@  int thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp)
 }
 EXPORT_SYMBOL_GPL(thermal_zone_get_temp);
 
-static void thermal_cdev_set_cur_state(struct thermal_cooling_device *cdev,
-				       int target)
+static int thermal_cdev_set_cur_state(struct thermal_cooling_device *cdev, int state)
 {
-	if (cdev->ops->set_cur_state(cdev, target))
-		return;
+	int ret;
+
+	/*
+	 * No check is needed for the ops->set_cur_state as the
+	 * registering function checked the ops are correctly set
+	 */
+	ret = cdev->ops->set_cur_state(cdev, state);
+	if (!ret) {
+		thermal_notify_cdev_state_update(cdev->id, state);
+		thermal_cooling_device_stats_update(cdev, state);
+		thermal_debug_cdev_state_update(cdev, state);
+	}
 
-	thermal_notify_cdev_state_update(cdev->id, target);
-	thermal_cooling_device_stats_update(cdev, target);
+	return ret;
 }
 
 void __thermal_cdev_update(struct thermal_cooling_device *cdev)
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 0ea99f50d57c..8461f008c3de 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -32,6 +32,7 @@ 
 struct thermal_zone_device;
 struct thermal_cooling_device;
 struct thermal_instance;
+struct thermal_debugfs;
 struct thermal_attr;
 
 enum thermal_trend {
@@ -110,6 +111,9 @@  struct thermal_cooling_device {
 	struct mutex lock; /* protect thermal_instances list */
 	struct list_head thermal_instances;
 	struct list_head node;
+#ifdef CONFIG_THERMAL_DEBUGFS
+	struct thermal_debugfs *debugfs;
+#endif
 };
 
 /**
@@ -183,6 +187,9 @@  struct thermal_zone_device {
 	struct list_head node;
 	struct delayed_work poll_queue;
 	enum thermal_notify_event notify_event;
+#ifdef CONFIG_THERMAL_DEBUGFS
+	struct thermal_debugfs *debugfs;
+#endif
 };
 
 /**