Message-Id: <20220406220809.22555-2-lukasz.luba@arm.com>
Date:   Wed,  6 Apr 2022 23:08:05 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     linux-kernel@...r.kernel.org
Cc:     lukasz.luba@....com, dietmar.eggemann@....com,
        viresh.kumar@...aro.org, rafael@...nel.org,
        daniel.lezcano@...aro.org, amitk@...nel.org, rui.zhang@...el.com,
        amit.kachhap@...il.com, linux-pm@...r.kernel.org
Subject: [RFC PATCH v3 1/5] cpufreq: stats: Introduce Cpufreq Active Stats

Introduce a new centralized mechanism for gathering and maintaining CPU
performance statistics accounting the active period of CPU. It tracks the
CPU activity at all performance levels (frequencies) taking into account
the idle entry/exit. This combined information can be used by other kernel
subsystems, like thermal governor, which tries to estimate the CPU
performance. The information about frequency change comes from CPUFreq
framework and the idle entry/exit event from CPUIdle framework.

Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 MAINTAINERS                     |   2 +-
 drivers/cpufreq/cpufreq_stats.c | 872 ++++++++++++++++++++++++++++++++
 include/linux/cpufreq_stats.h   | 131 +++++
 3 files changed, 1004 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/cpufreq_stats.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 9832b607e2e2..2c1b3b81b7df 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4991,7 +4991,7 @@ F:	Documentation/admin-guide/pm/intel_pstate.rst
 F:	Documentation/cpu-freq/
 F:	Documentation/devicetree/bindings/cpufreq/
 F:	drivers/cpufreq/
-F:	include/linux/cpufreq.h
+F:	include/linux/cpufreq*.h
 F:	include/linux/sched/cpufreq.h
 F:	kernel/sched/cpufreq*.c
 F:	tools/testing/selftests/cpufreq/
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 1570d6f3e75d..0ac57a2f24ed 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -12,6 +12,20 @@
 #include <linux/sched/clock.h>
 #include <linux/slab.h>
 
+#include <linux/cpufreq_stats.h>
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/cpumask.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/ktime.h>
+#include <linux/minmax.h>
+#include <linux/percpu.h>
+#include <linux/pm_opp.h>
+#include <linux/sched/clock.h>
+#include <linux/slab.h>
+
 struct cpufreq_stats {
 	unsigned int total_trans;
 	unsigned long long last_time;
@@ -27,6 +41,8 @@ struct cpufreq_stats {
 	unsigned long long reset_time;
 };
 
+static void cpufreq_active_stats_init(struct cpufreq_policy *policy);
+
 static void cpufreq_stats_update(struct cpufreq_stats *stats,
 				 unsigned long long time)
 {
@@ -252,6 +268,8 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy)
 	stats->last_time = local_clock();
 	stats->last_index = freq_table_get_index(stats, policy->cur);
 
+	cpufreq_active_stats_init(policy);
+
 	policy->stats = stats;
 	if (!sysfs_create_group(&policy->kobj, &stats_attr_group))
 		return;
@@ -287,4 +305,858 @@ void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
 	stats->last_index = new_index;
 	stats->trans_table[old_index * stats->max_state + new_index]++;
 	stats->total_trans++;
+
+	cpufreq_active_stats_cpu_freq_change(policy->cpu, new_freq);
+}
+
+static DEFINE_PER_CPU(struct cpufreq_active_stats *, ast_local);
+static bool cpu_hotplug_notification;
+
+static struct cpufreq_active_stats_state *alloc_state_stats(int count);
+static void update_local_stats(struct cpufreq_active_stats *ast, ktime_t event_ts);
+static void get_stats_snapshot(struct cpufreq_active_stats *ast);
+
+#ifdef CONFIG_DEBUG_FS
+static struct dentry *rootdir;
+
+static int cpufreq_active_stats_debug_residency_show(struct seq_file *s, void *unused)
+{
+	struct cpufreq_active_stats *ast = s->private;
+	u64 ts, residency;
+	int i;
+
+	ts = local_clock();
+
+	/*
+	 * Print statistics for each performance state and related residency
+	 * time [ns].
+	 */
+	for (i = 0; i < ast->states_count; i++) {
+		residency = ast->snapshot.result->residency[i];
+		if (i == ast->snapshot.result->last_freq_idx && !ast->in_idle && !ast->offline)
+			residency += ts - ast->snapshot.result->last_event_ts;
+
+		seq_printf(s, "%u:\t%llu\n", ast->freq[i], residency);
+	}
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(cpufreq_active_stats_debug_residency);
+
+static void cpufreq_active_stats_debug_init(int cpu)
+{
+	struct device *dev;
+	struct dentry *d;
+
+	if (!rootdir)
+		rootdir = debugfs_create_dir("cpufreq_active_stats", NULL);
+
+	dev = get_cpu_device(cpu);
+	if (!dev)
+		return;
+
+	d = debugfs_create_dir(dev_name(dev), rootdir);
+	debugfs_create_file("time_in_state", 0444, d,
+			    per_cpu(ast_local, cpu),
+			    &cpufreq_active_stats_debug_residency_fops);
+}
+
+static void cpufreq_active_stats_debug_remove(int cpu)
+{
+	struct dentry *debug_dir;
+	struct device *dev;
+
+	dev = get_cpu_device(cpu);
+	if (!dev || !rootdir)
+		return;
+
+	debug_dir = debugfs_lookup(dev_name(dev), rootdir);
+	debugfs_remove_recursive(debug_dir);
+}
+#else /* CONFIG_DEBUG_FS */
+static void cpufreq_active_stats_debug_init(int cpu) {}
+static void cpufreq_active_stats_debug_remove(int cpu) {}
+#endif
+
+static int get_freq_index(struct cpufreq_active_stats *ast, unsigned int freq)
+{
+	int i;
+
+	for (i = 0; i < ast->states_count; i++)
+		if (ast->freq[i] == freq)
+			return i;
+	return -EINVAL;
+}
+
+static void free_state_stats(struct cpufreq_active_stats_state *stats)
+{
+	if (!stats)
+		return;
+
+	kfree(stats->residency);
+	kfree(stats);
+}
+
+static void cpufreq_active_stats_deactivate(struct cpufreq_active_stats *ast)
+{
+	mutex_lock(&ast->activation_lock);
+
+	ast->num_clients--;
+	if (!ast->num_clients)
+		WRITE_ONCE(ast->activated, false);
+
+	/* Do similar accouning for shared structure and not deeper */
+	if (ast->shared_ast)
+		cpufreq_active_stats_deactivate(ast->shared_ast);
+
+	mutex_unlock(&ast->activation_lock);
+}
+
+static void cpufreq_active_stats_reinit_snapshots(struct cpufreq_active_stats *ast, int cpu)
+{
+	int size = ast->states_size;
+	unsigned long freq;
+	int curr_freq_idx;
+	u64 curr_ts;
+
+	freq = cpufreq_quick_get(cpu);
+	curr_freq_idx = get_freq_index(ast, freq);
+	if (curr_freq_idx < 0)
+		curr_freq_idx = 0;
+
+	curr_ts = local_clock();
+
+	/* Only idle stats have the 'curr' and 'prev' */
+	if (ast->shared_ast) {
+		ast->snapshot.curr->last_event_ts = curr_ts;
+		ast->snapshot.curr->last_freq_idx = curr_freq_idx;
+
+		ast->snapshot.prev->last_freq_idx = curr_freq_idx;
+		ast->snapshot.prev->last_event_ts = curr_ts;
+
+		memcpy(ast->snapshot.prev->residency,
+		       ast->snapshot.curr->residency, size);
+	}
+
+	ast->snapshot.result->last_event_ts = curr_ts;
+	ast->snapshot.result->last_freq_idx = curr_freq_idx;
+}
+
+static void cpufreq_active_stats_activate(struct cpufreq_active_stats *ast, int cpu)
+{
+	mutex_lock(&ast->activation_lock);
+
+	ast->num_clients++;
+	if (!READ_ONCE(ast->activated)) {
+		/* For idle tracking stats take snapshot of freq stats */
+		if (ast->shared_ast) {
+			get_stats_snapshot(ast);
+			ast->in_idle = idle_cpu(cpu);
+		}
+
+		cpufreq_active_stats_reinit_snapshots(ast, cpu);
+		WRITE_ONCE(ast->activated, true);
+	}
+
+	mutex_unlock(&ast->activation_lock);
+}
+
+/**
+ * cpufreq_active_stats_setup - setup stats monitor structures
+ * @cpu:	CPU id for which the update is done
+ *
+ * Setup Active Stats Monitor statistics for a given @cpu. It allocates the
+ * needed structures for tracking the CPU performance levels residency.
+ * Return a valid pointer to struct cpufreq_active_stats_monitor or corresponding
+ * ERR_PTR().
+ */
+struct cpufreq_active_stats_monitor *cpufreq_active_stats_setup(int cpu)
+{
+	struct cpufreq_active_stats_monitor *ast_mon;
+	struct cpufreq_active_stats *ast;
+
+	ast = per_cpu(ast_local, cpu);
+	if (!ast)
+		return ERR_PTR(-EINVAL);
+
+	ast_mon = kzalloc(sizeof(struct cpufreq_active_stats_monitor), GFP_KERNEL);
+	if (!ast_mon)
+		return ERR_PTR(-ENOMEM);
+
+	ast_mon->snapshot.result = alloc_state_stats(ast->states_count);
+	if (!ast_mon->snapshot.result)
+		goto free_ast_mon;
+
+	ast_mon->snapshot.curr = alloc_state_stats(ast->states_count);
+	if (!ast_mon->snapshot.curr)
+		goto free_local;
+
+	ast_mon->snapshot.prev = alloc_state_stats(ast->states_count);
+	if (!ast_mon->snapshot.prev)
+		goto free_snapshot_curr;
+
+	ast_mon->tmp_view.result = alloc_state_stats(ast->states_count);
+	if (!ast_mon->tmp_view.result)
+		goto free_snapshot_prev;
+
+	ast_mon->tmp_view.curr = alloc_state_stats(ast->states_count);
+	if (!ast_mon->tmp_view.curr)
+		goto free_tmp_view_result;
+
+	ast_mon->tmp_view.prev = alloc_state_stats(ast->states_count);
+	if (!ast_mon->tmp_view.prev)
+		goto free_tmp_view_snapshot_curr;
+
+	ast_mon->ast = ast;
+	ast_mon->local_period = 0;
+	ast_mon->states_count = ast->states_count;
+	ast_mon->states_size = ast->states_count * sizeof(u64);
+	ast_mon->cpu = cpu;
+
+	cpufreq_active_stats_activate(ast->shared_ast, cpu);
+	cpufreq_active_stats_activate(ast, cpu);
+
+	mutex_init(&ast_mon->lock);
+
+	return ast_mon;
+
+free_tmp_view_snapshot_curr:
+	free_state_stats(ast_mon->tmp_view.curr);
+free_tmp_view_result:
+	free_state_stats(ast_mon->tmp_view.result);
+free_snapshot_prev:
+	free_state_stats(ast_mon->snapshot.prev);
+free_snapshot_curr:
+	free_state_stats(ast_mon->snapshot.curr);
+free_local:
+	free_state_stats(ast_mon->snapshot.result);
+free_ast_mon:
+	kfree(ast_mon);
+
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_setup);
+
+/**
+ * cpufreq_active_stats_cpu_free_monitor - free Active Stats Monitor structures
+ * @ast_mon:	Active Stats Monitor pointer
+ *
+ * Free the Active Stats Monitor data structures. No return value.
+ */
+void cpufreq_active_stats_cpu_free_monitor(struct cpufreq_active_stats_monitor *ast_mon)
+{
+	if (IS_ERR_OR_NULL(ast_mon))
+		return;
+
+	cpufreq_active_stats_deactivate(ast_mon->ast);
+
+	free_state_stats(ast_mon->tmp_view.prev);
+	free_state_stats(ast_mon->tmp_view.curr);
+	free_state_stats(ast_mon->tmp_view.result);
+	free_state_stats(ast_mon->snapshot.prev);
+	free_state_stats(ast_mon->snapshot.curr);
+	free_state_stats(ast_mon->snapshot.result);
+	kfree(ast_mon);
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_cpu_free_monitor);
+
+static int update_monitor_stats(struct cpufreq_active_stats_monitor *ast_mon)
+{
+	struct cpufreq_active_stats_state *snapshot_local, *origin_local;
+	struct cpufreq_active_stats_state *origin_freq, *snapshot_freq;
+	struct cpufreq_active_stats_state *origin_idle, *snapshot_idle;
+	unsigned long seq_freq, seq_idle;
+	struct cpufreq_active_stats *ast;
+	int size, cpu_in_idle;
+
+	ast = ast_mon->ast;
+	size = ast->states_size;
+
+	/*
+	 * Take a consistent snapshot of the statistics updated from other CPU
+	 * which might be changing the frequency for the whole domain.
+	 */
+	origin_freq = ast->shared_ast->snapshot.result;
+	snapshot_freq = ast_mon->tmp_view.curr;
+	do {
+		seq_freq = read_seqcount_begin(&ast->shared_ast->seqcount);
+
+		/*
+		 * Take a consistent snapshot of the statistics updated from other CPU
+		 * which might be toggling idle.
+		 */
+		origin_idle = ast->snapshot.prev;
+		snapshot_idle = ast_mon->tmp_view.prev;
+		origin_local = ast->snapshot.result;
+		snapshot_local = ast_mon->tmp_view.result;
+		do {
+			seq_idle = read_seqcount_begin(&ast->seqcount);
+
+			memcpy(snapshot_idle->residency, origin_idle->residency, size);
+			snapshot_idle->last_event_ts = origin_idle->last_event_ts;
+			snapshot_idle->last_freq_idx = origin_idle->last_freq_idx;
+
+			memcpy(snapshot_local->residency, origin_local->residency, size);
+			snapshot_local->last_event_ts = origin_local->last_event_ts;
+			snapshot_local->last_freq_idx = origin_local->last_freq_idx;
+
+			cpu_in_idle = ast->in_idle || ast->offline;
+		} while (read_seqcount_retry(&ast->seqcount, seq_idle));
+
+		/* Now take from frequency, which path is less often used */
+		memcpy(snapshot_freq->residency, origin_freq->residency, size);
+		snapshot_freq->last_event_ts = origin_freq->last_event_ts;
+		snapshot_freq->last_freq_idx = origin_freq->last_freq_idx;
+
+	} while (read_seqcount_retry(&ast->shared_ast->seqcount, seq_freq));
+
+	return cpu_in_idle;
+}
+
+/**
+ * cpufreq_active_stats_cpu_update_monitor - update Active Stats Monitor structures
+ * @ast_mon:	Active Stats Monitor pointer
+ *
+ * Update Active Stats Monitor statistics for a given @ast_mon. It calculates
+ * residency time for all supported performance levels when CPU was running.
+ * Return 0 for success or -EINVAL on error.
+ */
+int cpufreq_active_stats_cpu_update_monitor(struct cpufreq_active_stats_monitor *ast_mon)
+{
+	struct cpufreq_active_stats_state *origin, *snapshot, *old, *local, *result;
+	int last_local_freq_idx, last_new_freq_idx;
+	int size, i, cpu_in_idle;
+	struct cpufreq_active_stats *ast;
+	s64 total_residency = 0;
+	u64 local_last_event_ts;
+	u64 last_event_ts = 0;
+	s64 period = 0;
+	s64 diff, acc;
+	u64 curr_ts;
+
+	if (IS_ERR_OR_NULL(ast_mon))
+		return -EINVAL;
+
+	ast = ast_mon->ast;
+
+	size = ast_mon->states_size;
+	origin = ast_mon->ast->snapshot.result;
+	local = ast_mon->snapshot.result;
+
+	mutex_lock(&ast_mon->lock);
+
+	curr_ts = local_clock();
+
+	/* last_event_ts = local->last_event_ts; */
+
+	/* Use older buffer for upcoming newest data */
+	swap(ast_mon->snapshot.curr, ast_mon->snapshot.prev);
+
+	snapshot = ast_mon->snapshot.curr;
+	old = ast_mon->snapshot.prev;
+	result = ast_mon->tmp_view.result;
+
+
+	cpu_in_idle = update_monitor_stats(ast_mon);
+
+	if (!cpu_in_idle) {
+		/* Take difference since this freq is set */
+		last_event_ts = max(last_event_ts, ast_mon->tmp_view.curr->last_event_ts);
+		/* Or take difference since the idle CPU last time accounted it if it was later */
+		last_event_ts = max(last_event_ts, result->last_event_ts);
+		diff = curr_ts - last_event_ts;
+
+		local_last_event_ts = ast_mon->tmp_view.result->last_event_ts;
+		period = curr_ts - local_last_event_ts;
+
+		last_new_freq_idx = ast_mon->tmp_view.curr->last_freq_idx;
+		last_local_freq_idx = ast_mon->tmp_view.result->last_freq_idx;
+
+		diff = max(0LL, diff);
+		if (diff > 0) {
+			result->residency[last_new_freq_idx] += diff;
+			total_residency += diff;
+		}
+		/* Calculate the difference for freq snapshot with idle snapshot */
+		for (i = 0; i < ast_mon->states_count; i++) {
+
+			acc = ast_mon->tmp_view.curr->residency[i];
+			acc -= ast_mon->tmp_view.prev->residency[i];
+
+			if (last_local_freq_idx != i) {
+				result->residency[i] += acc;
+				total_residency += acc;
+			}
+		}
+
+		/* Don't account twice the same running period */
+		result->residency[last_local_freq_idx] += period - total_residency;
+	}
+
+	memcpy(snapshot->residency, result->residency, size);
+
+	/* Calculate the difference of the running time since last check */
+	for (i = 0; i < ast_mon->states_count; i++) {
+		diff = snapshot->residency[i] - old->residency[i];
+		/* Avoid CPUs local clock differences issue and set 0 */
+		local->residency[i] = diff > 0 ? diff : 0;
+	}
+
+	snapshot->last_event_ts = curr_ts;
+	local->last_event_ts = curr_ts;
+	ast_mon->local_period = snapshot->last_event_ts - old->last_event_ts;
+
+	mutex_unlock(&ast_mon->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_cpu_update_monitor);
+
+static void get_stats_snapshot(struct cpufreq_active_stats *ast)
+{
+	struct cpufreq_active_stats_state *origin, *snapshot;
+	int size = ast->states_size;
+	unsigned long seq;
+
+	origin = ast->shared_ast->snapshot.result;
+	snapshot = ast->snapshot.curr;
+
+	/*
+	 * Take a consistent snapshot of the statistics updated from other CPU
+	 * which might be changing the frequency for the whole domain.
+	 */
+	do {
+		seq = read_seqcount_begin(&ast->shared_ast->seqcount);
+
+		memcpy(snapshot->residency, origin->residency, size);
+
+		snapshot->last_event_ts = origin->last_event_ts;
+		snapshot->last_freq_idx = origin->last_freq_idx;
+
+	} while (read_seqcount_retry(&ast->shared_ast->seqcount, seq));
+}
+
+static void
+update_local_stats(struct cpufreq_active_stats *ast, ktime_t event_ts)
+{
+	s64 total_residency = 0;
+	s64 diff, acc, period;
+	ktime_t prev_ts;
+	u64 prev;
+	int i;
+
+	get_stats_snapshot(ast);
+
+	prev = max(ast->snapshot.result->last_event_ts, ast->snapshot.curr->last_event_ts);
+	prev_ts = ns_to_ktime(prev);
+	diff = ktime_sub(event_ts, prev_ts);
+
+	prev_ts = ns_to_ktime(ast->snapshot.result->last_event_ts);
+	period = ktime_sub(event_ts, prev_ts);
+
+	i = ast->snapshot.curr->last_freq_idx;
+
+	diff = max(0LL, diff);
+	if (diff > 0) {
+		ast->snapshot.result->residency[i] += diff;
+		total_residency += diff;
+	}
+
+	for (i = 0; i < ast->states_count; i++) {
+		if (ast->snapshot.result->last_freq_idx == i)
+			continue;
+
+		acc = ast->snapshot.curr->residency[i];
+		acc -= ast->snapshot.prev->residency[i];
+		ast->snapshot.result->residency[i] += acc;
+		total_residency += acc;
+	}
+
+	/* Don't account twice the same running period */
+	i = ast->snapshot.result->last_freq_idx;
+	ast->snapshot.result->residency[i] += period - total_residency;
+
+	ast->snapshot.result->last_freq_idx = ast->snapshot.curr->last_freq_idx;
+
+	ast->snapshot.prev->last_freq_idx = ast->snapshot.curr->last_freq_idx;
+	ast->snapshot.prev->last_event_ts = ast->snapshot.curr->last_event_ts;
+
+	swap(ast->snapshot.curr, ast->snapshot.prev);
+
+	ast->snapshot.result->last_event_ts = event_ts;
+}
+
+static inline
+void _cpufreq_active_stats_cpu_idle_enter(struct cpufreq_active_stats *ast, ktime_t enter_ts)
+{
+	write_seqcount_begin(&ast->seqcount);
+
+	update_local_stats(ast, enter_ts);
+	ast->in_idle = true;
+
+	write_seqcount_end(&ast->seqcount);
+}
+
+static inline
+void _cpufreq_active_stats_cpu_idle_exit(struct cpufreq_active_stats *ast, ktime_t time_end)
+{
+	int size = ast->states_size;
+
+	write_seqcount_begin(&ast->seqcount);
+
+	get_stats_snapshot(ast);
+
+	ast->snapshot.result->last_freq_idx = ast->snapshot.curr->last_freq_idx;
+
+	memcpy(ast->snapshot.prev->residency, ast->snapshot.curr->residency, size);
+	ast->snapshot.prev->last_freq_idx = ast->snapshot.curr->last_freq_idx;
+	ast->snapshot.prev->last_event_ts = ast->snapshot.curr->last_event_ts;
+
+	swap(ast->snapshot.curr, ast->snapshot.prev);
+
+	ast->snapshot.result->last_event_ts = time_end;
+	ast->in_idle = false;
+
+	write_seqcount_end(&ast->seqcount);
+}
+
+/**
+ * cpufreq_active_stats_cpu_idle_enter - update Active Stats idle tracking data
+ * @enter_ts:	the time stamp with idle enter value
+ *
+ * Update the maintained statistics for entering idle for a given CPU.
+ * No return value.
+ */
+void cpufreq_active_stats_cpu_idle_enter(ktime_t enter_ts)
+{
+	struct cpufreq_active_stats *ast;
+
+	ast = per_cpu(ast_local, raw_smp_processor_id());
+	if (!ast || !READ_ONCE(ast->activated))
+		return;
+
+	_cpufreq_active_stats_cpu_idle_enter(ast, enter_ts);
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_cpu_idle_enter);
+
+/**
+ * cpufreq_active_stats_cpu_idle_exit - update Active Stats idle tracking data
+ * @time_end:	the time stamp with idle exit value
+ *
+ * Update the maintained statistics for exiting idle for a given CPU.
+ * No return value.
+ */
+void cpufreq_active_stats_cpu_idle_exit(ktime_t time_end)
+{
+	struct cpufreq_active_stats *ast;
+
+	ast = per_cpu(ast_local, raw_smp_processor_id());
+	if (!ast || !READ_ONCE(ast->activated))
+		return;
+
+	_cpufreq_active_stats_cpu_idle_exit(ast, time_end);
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_cpu_idle_exit);
+
+static void _cpufreq_active_stats_cpu_freq_change(struct cpufreq_active_stats *shared_ast,
+					  unsigned int freq, u64 ts)
+{
+	int prev_idx, next_idx;
+	s64 time_diff;
+
+	next_idx = get_freq_index(shared_ast, freq);
+	if (next_idx < 0)
+		return;
+
+	write_seqcount_begin(&shared_ast->seqcount);
+
+	/* The value in prev_idx is always a valid array index */
+	prev_idx = shared_ast->snapshot.result->last_freq_idx;
+
+	time_diff = ts - shared_ast->snapshot.result->last_event_ts;
+
+	/* Avoid jitter from different CPUs local clock */
+	if (time_diff > 0)
+		shared_ast->snapshot.result->residency[prev_idx] += time_diff;
+
+	shared_ast->snapshot.result->last_freq_idx = next_idx;
+	shared_ast->snapshot.result->last_event_ts = ts;
+
+	write_seqcount_end(&shared_ast->seqcount);
+}
+
+/**
+ * cpufreq_active_stats_cpu_freq_fast_change - update Active Stats tracking data
+ * @cpu:	the CPU id belonging to frequency domain which is updated
+ * @freq:	new frequency value
+ *
+ * Update the maintained statistics for frequency change for a given CPU's
+ * frequency domain. This function must be used only in the fast switch code
+ * path. No return value.
+ */
+void cpufreq_active_stats_cpu_freq_fast_change(int cpu, unsigned int freq)
+{
+	struct cpufreq_active_stats *ast;
+	u64 ts;
+
+	ast = per_cpu(ast_local, cpu);
+	if (!ast || !READ_ONCE(ast->activated))
+		return;
+
+	ts = local_clock();
+	_cpufreq_active_stats_cpu_freq_change(ast->shared_ast, freq, ts);
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_cpu_freq_fast_change);
+
+/**
+ * cpufreq_active_stats_cpu_freq_change - update Active Stats tracking data
+ * @cpu:	the CPU id belonging to frequency domain which is updated
+ * @freq:	new frequency value
+ *
+ * Update the maintained statistics for frequency change for a given CPU's
+ * frequency domain. This function must not be used in the fast switch code
+ * path. No return value.
+ */
+void cpufreq_active_stats_cpu_freq_change(int cpu, unsigned int freq)
+{
+	struct cpufreq_active_stats *ast, *shared_ast;
+	unsigned long flags;
+	u64 ts;
+
+	ast = per_cpu(ast_local, cpu);
+	if (!ast || !READ_ONCE(ast->activated))
+		return;
+
+	shared_ast = ast->shared_ast;
+	ts = local_clock();
+
+	spin_lock_irqsave(&shared_ast->lock, flags);
+	_cpufreq_active_stats_cpu_freq_change(shared_ast, freq, ts);
+	spin_unlock_irqrestore(&shared_ast->lock, flags);
+}
+EXPORT_SYMBOL_GPL(cpufreq_active_stats_cpu_freq_change);
+
+static struct cpufreq_active_stats_state *alloc_state_stats(int count)
+{
+	struct cpufreq_active_stats_state *stats;
+
+	stats = kzalloc(sizeof(*stats), GFP_KERNEL);
+	if (!stats)
+		return NULL;
+
+	stats->residency = kcalloc(count, sizeof(u64), GFP_KERNEL);
+	if (!stats->residency)
+		goto free_stats;
+
+	return stats;
+
+free_stats:
+	kfree(stats);
+
+	return NULL;
+}
+
+static struct cpufreq_active_stats *
+cpufreq_active_stats_init_struct(int cpu, int nr_opp, struct cpufreq_active_stats *shared_ast)
+{
+	struct cpufreq_active_stats *ast;
+	struct device *cpu_dev;
+	struct dev_pm_opp *opp;
+	unsigned long rate;
+	int i;
+
+	cpu_dev = get_cpu_device(cpu);
+	if (!cpu_dev) {
+		pr_err("%s: too early to get CPU%d device!\n",
+		       __func__, cpu);
+		return NULL;
+	}
+
+	ast = kzalloc(sizeof(*ast), GFP_KERNEL);
+	if (!ast)
+		return NULL;
+
+	ast->states_count = nr_opp;
+	ast->states_size = ast->states_count * sizeof(u64);
+	ast->in_idle = true;
+
+	ast->snapshot.result = alloc_state_stats(nr_opp);
+	if (!ast->snapshot.result)
+		goto free_ast;
+
+	if (!shared_ast) {
+		ast->freq = kcalloc(nr_opp, sizeof(unsigned long), GFP_KERNEL);
+		if (!ast->freq)
+			goto free_ast_local;
+
+		for (i = 0, rate = 0; i < nr_opp; i++, rate++) {
+			opp = dev_pm_opp_find_freq_ceil(cpu_dev, &rate);
+			if (IS_ERR(opp)) {
+				dev_warn(cpu_dev, "reading an OPP failed\n");
+				kfree(ast->freq);
+				goto free_ast_local;
+			}
+			dev_pm_opp_put(opp);
+
+			ast->freq[i] = rate / 1000;
+		}
+
+		/* Frequency isn't known at this point */
+		ast->snapshot.result->last_freq_idx = nr_opp - 1;
+	} else {
+		ast->freq = shared_ast->freq;
+
+		ast->snapshot.curr = alloc_state_stats(nr_opp);
+		if (!ast->snapshot.curr)
+			goto free_ast_local;
+
+		ast->snapshot.prev = alloc_state_stats(nr_opp);
+		if (!ast->snapshot.prev)
+			goto free_ast_snapshot;
+
+		ast->snapshot.curr->last_freq_idx = nr_opp - 1;
+		ast->snapshot.prev->last_freq_idx = nr_opp - 1;
+
+		ast->snapshot.result->last_freq_idx = nr_opp - 1;
+	}
+
+	mutex_init(&ast->activation_lock);
+	spin_lock_init(&ast->lock);
+	seqcount_init(&ast->seqcount);
+
+	return ast;
+
+free_ast_snapshot:
+	free_state_stats(ast->snapshot.curr);
+free_ast_local:
+	free_state_stats(ast->snapshot.result);
+free_ast:
+	kfree(ast);
+
+	return NULL;
+}
+
+static int cpuhp_cpufreq_stats_cpu_offline(unsigned int cpu)
+{
+	struct cpufreq_active_stats *ast;
+
+	ast = per_cpu(ast_local, cpu);
+	if (!ast)
+		return 0;
+
+	ast->offline = true;
+
+	if (!READ_ONCE(ast->activated))
+		return 0;
+
+	_cpufreq_active_stats_cpu_idle_enter(ast, local_clock());
+
+	return 0;
+}
+
+static int cpuhp_cpufreq_stats_cpu_online(unsigned int cpu)
+{
+	struct cpufreq_active_stats *ast;
+
+	ast = per_cpu(ast_local, cpu);
+	if (!ast)
+		return 0;
+
+	ast->offline = false;
+
+	if (!READ_ONCE(ast->activated))
+		return 0;
+
+	_cpufreq_active_stats_cpu_idle_exit(ast, local_clock());
+
+	return 0;
+}
+
+static void cpufreq_active_stats_cleanup(struct cpufreq_active_stats *ast)
+{
+	free_state_stats(ast->snapshot.prev);
+	free_state_stats(ast->snapshot.curr);
+	free_state_stats(ast->snapshot.result);
+	kfree(ast);
+}
+
+static void cpufreq_active_stats_init(struct cpufreq_policy *policy)
+{
+	struct cpufreq_active_stats *ast, *shared_ast;
+	cpumask_var_t setup_cpus;
+	struct device *cpu_dev;
+	int nr_opp, cpu;
+
+	cpu = policy->cpu;
+	cpu_dev = get_cpu_device(cpu);
+	if (!cpu_dev) {
+		pr_err("%s: too early to get CPU%d device!\n",
+		       __func__, cpu);
+		return;
+	}
+
+	nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
+	if (nr_opp <= 0) {
+		dev_warn(cpu_dev, "OPP table is not ready\n");
+		return;
+	}
+
+	if (!alloc_cpumask_var(&setup_cpus, GFP_KERNEL)) {
+		dev_warn(cpu_dev, "cpumask alloc failed\n");
+		return;
+	}
+
+	shared_ast = cpufreq_active_stats_init_struct(cpu, nr_opp, NULL);
+	if (!shared_ast) {
+		free_cpumask_var(setup_cpus);
+		dev_warn(cpu_dev, "failed to setup shared_ast properly\n");
+		return;
+	}
+
+	for_each_cpu(cpu, policy->related_cpus) {
+		ast = cpufreq_active_stats_init_struct(cpu, nr_opp, shared_ast);
+		if (!ast) {
+			dev_warn(cpu_dev, "failed to setup stats properly\n");
+			goto cpus_cleanup;
+		}
+
+		ast->shared_ast = shared_ast;
+		per_cpu(ast_local, cpu) = ast;
+
+		cpufreq_active_stats_debug_init(cpu);
+
+		cpumask_set_cpu(cpu, setup_cpus);
+	}
+
+
+	if (!cpu_hotplug_notification) {
+		cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+				  "cpufreq_stats_cpu:online",
+				   cpuhp_cpufreq_stats_cpu_online,
+				   cpuhp_cpufreq_stats_cpu_offline);
+
+		cpu_hotplug_notification = true;
+	}
+
+	free_cpumask_var(setup_cpus);
+	dev_info(cpu_dev, "Cpufreq Active Stats created\n");
+
+	return;
+
+cpus_cleanup:
+	dev_warn(cpu_dev, "Cpufreq Active Stats setup failed\n");
+
+	for_each_cpu(cpu, setup_cpus) {
+		cpufreq_active_stats_debug_remove(cpu);
+
+		ast = per_cpu(ast_local, cpu);
+		per_cpu(ast_local, cpu) = NULL;
+
+		cpufreq_active_stats_cleanup(ast);
+	}
+
+	free_cpumask_var(setup_cpus);
+	kfree(shared_ast->freq);
+
+	cpufreq_active_stats_cleanup(shared_ast);
 }
diff --git a/include/linux/cpufreq_stats.h b/include/linux/cpufreq_stats.h
new file mode 100644
index 000000000000..0a207df9ebb0
--- /dev/null
+++ b/include/linux/cpufreq_stats.h
@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CPUFREQ_STATS_H
+#define _LINUX_CPUFREQ_STATS_H
+
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/seqlock.h>
+#include <linux/spinlock.h>
+
+/**
+ * cpufreq_active_stats_state - State statistics associated with perf. level
+ * @last_event_ts:	Timestamp of the last event in nanoseconds
+ * @last_freq_idx:	Last used frequency index
+ * @residency:		Array which holds total time (in nanoseconds) that
+ *			each frequency has been used when CPU was
+ *			running
+ */
+struct cpufreq_active_stats_state {
+	u64 last_event_ts;
+	int last_freq_idx;
+	u64 *residency;
+};
+
+/**
+ * cpufreq_active_stats_snapshot - Cpufreq Active Stats Snapshot structure
+ * @curr:	Snapshot of statistics from Active Stats main structure
+ *		which accounts this CPU performance states residency
+ * @prev:	Old snapshot of the Active Stats main structure
+ *		structure, against which new snapshot is compared
+ * @result:	Statistics of running time for each performance state which
+ *		are calculated for this CPU for a specific period based on
+ *		@prev and @curr data.
+ */
+struct cpufreq_active_stats_snapshot {
+	struct cpufreq_active_stats_state *curr;
+	struct cpufreq_active_stats_state *prev;
+	struct cpufreq_active_stats_state *result;
+};
+
+/**
+ * cpufreq_active_stats - Cpufreq Active Stats main structure
+ * @activated:	Set when the tracking mechanism is used
+ * @num_clients:	Number of clients using tracking mechanism
+ * @in_ilde:	Set when CPU is in idle
+ * @offline:	Set when CPU was hotplug out and is offline
+ * @states_count:	Number of state entries in the statistics
+ * @states_size:	Size of the state stats entries in bytes
+ * @freq:	Frequency table
+ * @local:	Statistics of running time which are calculated for this CPU
+ * @snapshot:	Snapshot of statistics which accounts the frequencies
+ *		residency combined with idle period
+ * @seqcount:	Used for making consistent state for the reader side
+ *		of this statistics data
+ */
+struct cpufreq_active_stats {
+	bool activated;
+	int num_clients;
+	bool in_idle;
+	bool offline;
+	unsigned int states_count;
+	unsigned int states_size;
+	unsigned int *freq;
+	struct cpufreq_active_stats_snapshot snapshot;
+	struct cpufreq_active_stats *shared_ast;
+	struct mutex activation_lock;
+	/* protect concurent cpufreq changes in slow path */
+	spinlock_t lock;
+	/* Seqcount to create consistent state in the read side */
+	seqcount_t seqcount;
+};
+
+/**
+ * cpufreq_active_stats_monitor - Active Stats Monitor structure
+ * @local_period:	Local period for which the statistics are provided
+ * @states_count:	Number of state entries in the statistics
+ * @states_size:	Size of the state stats entries in bytes
+ * @ast:	Active Stats structure for the associated CPU, which is used
+ *		for taking the snapshot
+ * @snapshot:	Snapshot of statistics which accounts for this private monitor
+ *		period the frequencies residency combined with idle
+ * @tmp_view:	Snapshot of statistics which is used for calculating local
+ *		monitor statistics for private period the frequencies
+ *		residency combined with idle
+ * @lock:	Lock which is used to serialize access to Active Stats
+ *		Monitor structure which might be used concurrently.
+ */
+struct cpufreq_active_stats_monitor {
+	int cpu;
+	u64 local_period;
+	unsigned int states_count;
+	unsigned int states_size;
+	struct cpufreq_active_stats *ast;
+	struct cpufreq_active_stats_snapshot snapshot;
+	struct cpufreq_active_stats_snapshot tmp_view;
+	struct mutex lock;
+};
+
+#if defined(CONFIG_CPU_FREQ_STAT)
+void cpufreq_active_stats_cpu_idle_enter(ktime_t time_start);
+void cpufreq_active_stats_cpu_idle_exit(ktime_t time_start);
+void cpufreq_active_stats_cpu_freq_fast_change(int cpu, unsigned int freq);
+void cpufreq_active_stats_cpu_freq_change(int cpu, unsigned int freq);
+struct cpufreq_active_stats_monitor *cpufreq_active_stats_setup(int cpu);
+void cpufreq_active_stats_cpu_free_monitor(struct cpufreq_active_stats_monitor *ast_mon);
+int cpufreq_active_stats_cpu_update_monitor(struct cpufreq_active_stats_monitor *ast_mon);
+#else
+static inline
+void cpufreq_active_stats_cpu_freq_fast_change(int cpu, unsigned int freq) {}
+static inline
+void cpufreq_active_stats_cpu_freq_change(int cpu, unsigned int freq) {}
+static inline
+void cpufreq_active_stats_cpu_idle_enter(ktime_t time_start) {}
+static inline
+void cpufreq_active_stats_cpu_idle_exit(ktime_t time_start) {}
+static inline
+struct cpufreq_active_stats_monitor *cpufreq_active_stats_setup(int cpu)
+{
+	return ERR_PTR(-EINVAL);
+}
+static inline
+void cpufreq_active_stats_cpu_free_monitor(struct cpufreq_active_stats_monitor *ast_mon)
+{
+}
+static inline
+int cpufreq_active_stats_cpu_update_monitor(struct cpufreq_active_stats_monitor *ast_mon)
+{
+	return -EINVAL;
+}
+#endif
+
+#endif /* _LINUX_CPUFREQ_STATS_H */
-- 
2.17.1

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