[PATCH v2 3/4] thermal/drivers/intel_powerclamp: Use powercap idle-inject framework

[Srinivas Pandruvada]

There are two idle injection implementation in the Linux kernel. One
via intel_powerclamp and the other using powercap/idle_inject. Both
implementation end up in calling play_idle* function from a FIFO
priority thread. Both can't be used at the same time.

Currently per core idle injection (cpuidle_cooling) is using
powercap/idle_inject, which is not used in platforms where
intel_powerclamp is used for system wide idle injection. So there is
no conflict. But there are some use cases where per core idle injection
is beneficial on the same system where system wide idle injection is
also used via intel_powerclamp. To avoid conflict only one of the idle
injection type must be in use at a time. This require a common framework
which both per core and system wide idle injection can use.

Here powercap/idle_inject can be used for both per-core and for system
wide idle injection. This framework has a well defined interface
which allow registry for per-core or for all CPUs (system wide). If
particular CPU is already participating in idle injection, the call
to registry fails. Here the registry can be done when user space
changes the current cooling device state.

Also one framework for idle injection is better as there is one loop
calling play_idle*, instead of multiple for better maintenance.

So, reuse powercap/idle_inject calls in intel_powerclamp. This simplifies
the code as all per CPU kthreads which calls play_idle* can be removed.

The changes include:
- Remove unneeded include files
- Remove per CPU kthread workers: balancing_work and idle_injection_work
- Reuse the compensation related code by moving from previous worker
thread to idle_injection callbacks
- Adjust the idle_duration and runtime by using powercap/idle_inject
interface
- Remove all variables, which are not required once powercap/idle_inject
is used
- Add mutex to avoid race during removal of idle injection during module
unload and user action to change idle inject percent
- Use READ_ONCE and WRITE_ONCE for data accessed from multiple CPUs

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
---
v2:
- Use idle_inject_register_full instead of idle_inject_register
- Also fix dependency issue with POWERCAP config
Reported-by: kernel test robot <lkp@xxxxxxxxx>

 drivers/thermal/intel/Kconfig            |   2 +
 drivers/thermal/intel/intel_powerclamp.c | 292 ++++++++++-------------
 2 files changed, 126 insertions(+), 168 deletions(-)

diff --git a/drivers/thermal/intel/Kconfig b/drivers/thermal/intel/Kconfig
index f0c845679250..6c2a95f41c81 100644
--- a/drivers/thermal/intel/Kconfig
+++ b/drivers/thermal/intel/Kconfig
@@ -3,6 +3,8 @@ config INTEL_POWERCLAMP
 	tristate "Intel PowerClamp idle injection driver"
 	depends on X86
 	depends on CPU_SUP_INTEL
+	select POWERCAP
+	select IDLE_INJECT
 	help
 	  Enable this to enable Intel PowerClamp idle injection driver. This
 	  enforce idle time which results in more package C-state residency. The
diff --git a/drivers/thermal/intel/intel_powerclamp.c b/drivers/thermal/intel/intel_powerclamp.c
index b80e25ec1261..3f2b20ae8f68 100644
--- a/drivers/thermal/intel/intel_powerclamp.c
+++ b/drivers/thermal/intel/intel_powerclamp.c
@@ -2,7 +2,7 @@
 /*
  * intel_powerclamp.c - package c-state idle injection
  *
- * Copyright (c) 2012, Intel Corporation.
+ * Copyright (c) 2022, Intel Corporation.
  *
  * Authors:
  *     Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
@@ -27,21 +27,15 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
-#include <linux/kthread.h>
 #include <linux/cpu.h>
 #include <linux/thermal.h>
-#include <linux/slab.h>
-#include <linux/tick.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
-#include <linux/sched/rt.h>
-#include <uapi/linux/sched/types.h>
+#include <linux/idle_inject.h>
 
-#include <asm/nmi.h>
 #include <asm/msr.h>
 #include <asm/mwait.h>
 #include <asm/cpu_device_id.h>
-#include <asm/hardirq.h>
 
 #define MAX_TARGET_RATIO (50U)
 /* For each undisturbed clamping period (no extra wake ups during idle time),
@@ -60,6 +54,7 @@ static struct dentry *debug_dir;
 
 /* user selected target */
 static unsigned int set_target_ratio;
+static bool target_ratio_updated;
 static unsigned int current_ratio;
 static bool should_skip;
 
@@ -67,26 +62,20 @@ static unsigned int control_cpu; /* The cpu assigned to collect stat and update
 				  * control parameters. default to BSP but BSP
 				  * can be offlined.
 				  */
-static bool clamping;
-
-struct powerclamp_worker_data {
-	struct kthread_worker *worker;
-	struct kthread_work balancing_work;
-	struct kthread_delayed_work idle_injection_work;
+struct powerclamp_data {
 	unsigned int cpu;
 	unsigned int count;
 	unsigned int guard;
 	unsigned int window_size_now;
 	unsigned int target_ratio;
-	unsigned int duration_jiffies;
 	bool clamping;
 };
 
-static struct powerclamp_worker_data __percpu *worker_data;
+static struct powerclamp_data powerclamp_data;
+
 static struct thermal_cooling_device *cooling_dev;
-static unsigned long *cpu_clamping_mask;  /* bit map for tracking per cpu
-					   * clamping kthread worker
-					   */
+
+static DEFINE_MUTEX(powerclamp_lock);
 
 static unsigned int duration;
 static unsigned int pkg_cstate_ratio_cur;
@@ -344,79 +333,33 @@ static bool powerclamp_adjust_controls(unsigned int target_ratio,
 	return set_target_ratio + guard <= current_ratio;
 }
 
-static void clamp_balancing_func(struct kthread_work *work)
+static unsigned int get_run_time(void)
 {
-	struct powerclamp_worker_data *w_data;
-	int sleeptime;
-	unsigned long target_jiffies;
 	unsigned int compensated_ratio;
-	int interval; /* jiffies to sleep for each attempt */
-
-	w_data = container_of(work, struct powerclamp_worker_data,
-			      balancing_work);
+	unsigned int runtime;
 
 	/*
 	 * make sure user selected ratio does not take effect until
 	 * the next round. adjust target_ratio if user has changed
 	 * target such that we can converge quickly.
 	 */
-	w_data->target_ratio = READ_ONCE(set_target_ratio);
-	w_data->guard = 1 + w_data->target_ratio / 20;
-	w_data->window_size_now = window_size;
-	w_data->duration_jiffies = msecs_to_jiffies(duration);
-	w_data->count++;
+	powerclamp_data.target_ratio = READ_ONCE(set_target_ratio);
+	powerclamp_data.guard = 1 + powerclamp_data.target_ratio / 20;
+	powerclamp_data.window_size_now = window_size;
 
 	/*
 	 * systems may have different ability to enter package level
 	 * c-states, thus we need to compensate the injected idle ratio
 	 * to achieve the actual target reported by the HW.
 	 */
-	compensated_ratio = w_data->target_ratio +
-		get_compensation(w_data->target_ratio);
+	compensated_ratio = powerclamp_data.target_ratio +
+		get_compensation(powerclamp_data.target_ratio);
 	if (compensated_ratio <= 0)
 		compensated_ratio = 1;
-	interval = w_data->duration_jiffies * 100 / compensated_ratio;
-
-	/* align idle time */
-	target_jiffies = roundup(jiffies, interval);
-	sleeptime = target_jiffies - jiffies;
-	if (sleeptime <= 0)
-		sleeptime = 1;
-
-	if (clamping && w_data->clamping && cpu_online(w_data->cpu))
-		kthread_queue_delayed_work(w_data->worker,
-					   &w_data->idle_injection_work,
-					   sleeptime);
-}
 
-static void clamp_idle_injection_func(struct kthread_work *work)
-{
-	struct powerclamp_worker_data *w_data;
-
-	w_data = container_of(work, struct powerclamp_worker_data,
-			      idle_injection_work.work);
+	runtime = duration * 100 / compensated_ratio - duration;
 
-	/*
-	 * only elected controlling cpu can collect stats and update
-	 * control parameters.
-	 */
-	if (w_data->cpu == control_cpu &&
-	    !(w_data->count % w_data->window_size_now)) {
-		should_skip =
-			powerclamp_adjust_controls(w_data->target_ratio,
-						   w_data->guard,
-						   w_data->window_size_now);
-		smp_mb();
-	}
-
-	if (should_skip)
-		goto balance;
-
-	play_idle(jiffies_to_usecs(w_data->duration_jiffies));
-
-balance:
-	if (clamping && w_data->clamping && cpu_online(w_data->cpu))
-		kthread_queue_work(w_data->worker, &w_data->balancing_work);
+	return runtime;
 }
 
 /*
@@ -452,104 +395,127 @@ static void poll_pkg_cstate(struct work_struct *dummy)
 	msr_last = msr_now;
 	tsc_last = tsc_now;
 
-	if (true == clamping)
+	if (powerclamp_data.clamping)
 		schedule_delayed_work(&poll_pkg_cstate_work, HZ);
 }
 
-static void start_power_clamp_worker(unsigned long cpu)
+static struct idle_inject_device *ii_dev;
+
+static int idle_inject_begin(unsigned int cpu)
 {
-	struct powerclamp_worker_data *w_data = per_cpu_ptr(worker_data, cpu);
-	struct kthread_worker *worker;
+	/*
+	 * only elected controlling cpu can collect stats and update
+	 * control parameters.
+	 */
+	if (cpu == control_cpu) {
+		bool update = READ_ONCE(target_ratio_updated);
+
+		if (!(powerclamp_data.count % powerclamp_data.window_size_now)) {
+			bool skip = powerclamp_adjust_controls(powerclamp_data.target_ratio,
+						       powerclamp_data.guard,
+						       powerclamp_data.window_size_now);
+			WRITE_ONCE(should_skip, skip);
+			update = true;
+		}
 
-	worker = kthread_create_worker_on_cpu(cpu, 0, "kidle_inj/%ld", cpu);
-	if (IS_ERR(worker))
-		return;
+		if (update) {
+			unsigned int runtime;
+
+			runtime = get_run_time();
+			idle_inject_set_duration(ii_dev, runtime, duration);
+			WRITE_ONCE(target_ratio_updated, false);
+		}
+		powerclamp_data.count++;
+	}
+
+	if (READ_ONCE(should_skip))
+		return -EAGAIN;
 
-	w_data->worker = worker;
-	w_data->count = 0;
-	w_data->cpu = cpu;
-	w_data->clamping = true;
-	set_bit(cpu, cpu_clamping_mask);
-	sched_set_fifo(worker->task);
-	kthread_init_work(&w_data->balancing_work, clamp_balancing_func);
-	kthread_init_delayed_work(&w_data->idle_injection_work,
-				  clamp_idle_injection_func);
-	kthread_queue_work(w_data->worker, &w_data->balancing_work);
+	return 0;
 }
 
-static void stop_power_clamp_worker(unsigned long cpu)
+static void trigger_idle_injection(void)
 {
-	struct powerclamp_worker_data *w_data = per_cpu_ptr(worker_data, cpu);
+	unsigned int runtime = get_run_time();
 
-	if (!w_data->worker)
-		return;
+	idle_inject_set_duration(ii_dev, runtime, duration);
+	idle_inject_start(ii_dev);
+	powerclamp_data.clamping = true;
+}
+
+static int powerclamp_idle_injection_register(void)
+{
+	static cpumask_t idle_injection_cpu_mask;
+	unsigned long cpu;
 
-	w_data->clamping = false;
-	/*
-	 * Make sure that all works that get queued after this point see
-	 * the clamping disabled. The counter part is not needed because
-	 * there is an implicit memory barrier when the queued work
-	 * is proceed.
-	 */
-	smp_wmb();
-	kthread_cancel_work_sync(&w_data->balancing_work);
-	kthread_cancel_delayed_work_sync(&w_data->idle_injection_work);
 	/*
-	 * The balancing work still might be queued here because
-	 * the handling of the "clapming" variable, cancel, and queue
-	 * operations are not synchronized via a lock. But it is not
-	 * a big deal. The balancing work is fast and destroy kthread
-	 * will wait for it.
+	 * The idle inject core will only inject for online CPUs,
+	 * So we can register for all present CPUs. In this way
+	 * if some CPU goes online/offline while idle inject
+	 * is registered, nothing additional calls are required.
+	 * The same runtime and idle time is applicable for
+	 * newly onlined CPUs if any.
 	 */
-	clear_bit(w_data->cpu, cpu_clamping_mask);
-	kthread_destroy_worker(w_data->worker);
+	for_each_present_cpu(cpu) {
+		cpumask_set_cpu(cpu, &idle_injection_cpu_mask);
+	}
+
+	ii_dev = idle_inject_register_full(&idle_injection_cpu_mask,
+					   idle_inject_begin, NULL);
+	if (!ii_dev) {
+		pr_err("powerclamp: idle_inject_register failed\n");
+		return -EAGAIN;
+	}
 
-	w_data->worker = NULL;
+	idle_inject_set_duration(ii_dev, TICK_USEC, duration);
+	idle_inject_set_latency(ii_dev, UINT_MAX);
+
+	return 0;
+}
+
+static void remove_idle_injection(void)
+{
+	if (!powerclamp_data.clamping)
+		return;
+
+	powerclamp_data.clamping = false;
+	idle_inject_stop(ii_dev);
 }
 
 static int start_power_clamp(void)
 {
-	unsigned long cpu;
+	int ret;
 
-	set_target_ratio = clamp(set_target_ratio, 0U, MAX_TARGET_RATIO - 1);
 	/* prevent cpu hotplug */
 	cpus_read_lock();
 
 	/* prefer BSP */
 	control_cpu = cpumask_first(cpu_online_mask);
 
-	clamping = true;
-	schedule_delayed_work(&poll_pkg_cstate_work, 0);
-
-	/* start one kthread worker per online cpu */
-	for_each_online_cpu(cpu) {
-		start_power_clamp_worker(cpu);
+	ret = powerclamp_idle_injection_register();
+	if (!ret) {
+		trigger_idle_injection();
+		schedule_delayed_work(&poll_pkg_cstate_work, 0);
 	}
+
 	cpus_read_unlock();
 
-	return 0;
+	return ret;
 }
 
 static void end_power_clamp(void)
 {
-	int i;
-
-	/*
-	 * Block requeuing in all the kthread workers. They will flush and
-	 * stop faster.
-	 */
-	clamping = false;
-	for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) {
-		pr_debug("clamping worker for cpu %d alive, destroy\n", i);
-		stop_power_clamp_worker(i);
+	if (powerclamp_data.clamping) {
+		remove_idle_injection();
+		idle_inject_unregister(ii_dev);
 	}
 }
 
 static int powerclamp_cpu_online(unsigned int cpu)
 {
-	if (clamping == false)
+	if (!powerclamp_data.clamping)
 		return 0;
-	start_power_clamp_worker(cpu);
+
 	/* prefer BSP as controlling CPU */
 	if (cpu == 0) {
 		control_cpu = 0;
@@ -560,10 +526,6 @@ static int powerclamp_cpu_online(unsigned int cpu)
 
 static int powerclamp_cpu_predown(unsigned int cpu)
 {
-	if (clamping == false)
-		return 0;
-
-	stop_power_clamp_worker(cpu);
 	if (cpu != control_cpu)
 		return 0;
 
@@ -585,7 +547,7 @@ static int powerclamp_get_max_state(struct thermal_cooling_device *cdev,
 static int powerclamp_get_cur_state(struct thermal_cooling_device *cdev,
 				 unsigned long *state)
 {
-	if (true == clamping)
+	if (powerclamp_data.clamping)
 		*state = pkg_cstate_ratio_cur;
 	else
 		/* to save power, do not poll idle ratio while not clamping */
@@ -599,24 +561,30 @@ static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev,
 {
 	int ret = 0;
 
+	mutex_lock(&powerclamp_lock);
+
 	new_target_ratio = clamp(new_target_ratio, 0UL,
-				(unsigned long) (MAX_TARGET_RATIO-1));
-	if (set_target_ratio == 0 && new_target_ratio > 0) {
+				(unsigned long) (MAX_TARGET_RATIO - 1));
+	if (READ_ONCE(set_target_ratio) == 0 && new_target_ratio > 0) {
 		pr_info("Start idle injection to reduce power\n");
-		set_target_ratio = new_target_ratio;
+		WRITE_ONCE(set_target_ratio, new_target_ratio);
 		ret = start_power_clamp();
+		if (ret)
+			WRITE_ONCE(set_target_ratio, 0);
 		goto exit_set;
-	} else	if (set_target_ratio > 0 && new_target_ratio == 0) {
+	} else	if (READ_ONCE(set_target_ratio) > 0 && new_target_ratio == 0) {
 		pr_info("Stop forced idle injection\n");
 		end_power_clamp();
-		set_target_ratio = 0;
+		WRITE_ONCE(set_target_ratio, 0);
+		WRITE_ONCE(target_ratio_updated, false);
 	} else	/* adjust currently running */ {
-		set_target_ratio = new_target_ratio;
-		/* make new set_target_ratio visible to other cpus */
-		smp_mb();
+		WRITE_ONCE(set_target_ratio, new_target_ratio);
+		WRITE_ONCE(target_ratio_updated, true);
 	}
 
 exit_set:
+	mutex_unlock(&powerclamp_lock);
+
 	return ret;
 }
 
@@ -686,14 +654,10 @@ static int __init powerclamp_init(void)
 {
 	int retval;
 
-	cpu_clamping_mask = bitmap_zalloc(num_possible_cpus(), GFP_KERNEL);
-	if (!cpu_clamping_mask)
-		return -ENOMEM;
-
 	/* probe cpu features and ids here */
 	retval = powerclamp_probe();
 	if (retval)
-		goto exit_free;
+		return retval;
 
 	/* set default limit, maybe adjusted during runtime based on feedback */
 	window_size = 2;
@@ -702,53 +666,45 @@ static int __init powerclamp_init(void)
 					   powerclamp_cpu_online,
 					   powerclamp_cpu_predown);
 	if (retval < 0)
-		goto exit_free;
+		return retval;
 
 	hp_state = retval;
 
-	worker_data = alloc_percpu(struct powerclamp_worker_data);
-	if (!worker_data) {
-		retval = -ENOMEM;
-		goto exit_unregister;
-	}
-
 	cooling_dev = thermal_cooling_device_register("intel_powerclamp", NULL,
-						&powerclamp_cooling_ops);
+						      &powerclamp_cooling_ops);
 	if (IS_ERR(cooling_dev)) {
 		retval = -ENODEV;
-		goto exit_free_thread;
+		goto exit_unregister;
 	}
 
 	if (!duration)
-		duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES);
+		duration = jiffies_to_usecs(DEFAULT_DURATION_JIFFIES);
 
 	powerclamp_create_debug_files();
 
 	return 0;
 
-exit_free_thread:
-	free_percpu(worker_data);
 exit_unregister:
 	cpuhp_remove_state_nocalls(hp_state);
-exit_free:
-	bitmap_free(cpu_clamping_mask);
 	return retval;
 }
 module_init(powerclamp_init);
 
 static void __exit powerclamp_exit(void)
 {
+	mutex_lock(&powerclamp_lock);
 	end_power_clamp();
+	mutex_unlock(&powerclamp_lock);
 	cpuhp_remove_state_nocalls(hp_state);
-	free_percpu(worker_data);
 	thermal_cooling_device_unregister(cooling_dev);
-	bitmap_free(cpu_clamping_mask);
 
 	cancel_delayed_work_sync(&poll_pkg_cstate_work);
 	debugfs_remove_recursive(debug_dir);
 }
 module_exit(powerclamp_exit);
 
+MODULE_IMPORT_NS(IDLE_INJECT);
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>");
 MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>");
-- 
2.31.1