Merge branch 'next' into for-linus

3 files changed, 163 insertions, 185 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 6e2ec0b1894..fd69086d08d 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -761,6 +761,10 @@ static struct kobj_type ktype_cpufreq = {
  * cpufreq_add_dev - add a CPU device
  *
  * Adds the cpufreq interface for a CPU device.
+ *
+ * The Oracle says: try running cpufreq registration/unregistration concurrently
+ * with with cpu hotplugging and all hell will break loose. Tried to clean this
+ * mess up, but more thorough testing is needed. - Mathieu
  */
 static int cpufreq_add_dev(struct sys_device *sys_dev)
 {
@@ -772,9 +776,6 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 	struct sys_device *cpu_sys_dev;
 	unsigned long flags;
 	unsigned int j;
-#ifdef CONFIG_SMP
-	struct cpufreq_policy *managed_policy;
-#endif
 
 	if (cpu_is_offline(cpu))
 		return 0;
@@ -804,15 +805,12 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 		goto nomem_out;
 	}
 	if (!alloc_cpumask_var(&policy->cpus, GFP_KERNEL)) {
-		kfree(policy);
 		ret = -ENOMEM;
-		goto nomem_out;
+		goto err_free_policy;
 	}
 	if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL)) {
-		free_cpumask_var(policy->cpus);
-		kfree(policy);
 		ret = -ENOMEM;
-		goto nomem_out;
+		goto err_free_cpumask;
 	}
 
 	policy->cpu = cpu;
@@ -820,7 +818,8 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 
 	/* Initially set CPU itself as the policy_cpu */
 	per_cpu(policy_cpu, cpu) = cpu;
-	lock_policy_rwsem_write(cpu);
+	ret = (lock_policy_rwsem_write(cpu) < 0);
+	WARN_ON(ret);
 
 	init_completion(&policy->kobj_unregister);
 	INIT_WORK(&policy->update, handle_update);
@@ -833,7 +832,7 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 	ret = cpufreq_driver->init(policy);
 	if (ret) {
 		dprintk("initialization failed\n");
-		goto err_out;
+		goto err_unlock_policy;
 	}
 	policy->user_policy.min = policy->min;
 	policy->user_policy.max = policy->max;
@@ -852,21 +851,31 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 #endif
 
 	for_each_cpu(j, policy->cpus) {
+		struct cpufreq_policy *managed_policy;
+
 		if (cpu == j)
 			continue;
 
 		/* Check for existing affected CPUs.
 		 * They may not be aware of it due to CPU Hotplug.
+		 * cpufreq_cpu_put is called when the device is removed
+		 * in __cpufreq_remove_dev()
 		 */
-		managed_policy = cpufreq_cpu_get(j);		/* FIXME: Where is this released?  What about error paths? */
+		managed_policy = cpufreq_cpu_get(j);
 		if (unlikely(managed_policy)) {
 
 			/* Set proper policy_cpu */
 			unlock_policy_rwsem_write(cpu);
 			per_cpu(policy_cpu, cpu) = managed_policy->cpu;
 
-			if (lock_policy_rwsem_write(cpu) < 0)
-				goto err_out_driver_exit;
+			if (lock_policy_rwsem_write(cpu) < 0) {
+				/* Should not go through policy unlock path */
+				if (cpufreq_driver->exit)
+					cpufreq_driver->exit(policy);
+				ret = -EBUSY;
+				cpufreq_cpu_put(managed_policy);
+				goto err_free_cpumask;
+			}
 
 			spin_lock_irqsave(&cpufreq_driver_lock, flags);
 			cpumask_copy(managed_policy->cpus, policy->cpus);
@@ -878,11 +887,13 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 						&managed_policy->kobj,
 						"cpufreq");
 			if (ret)
-				goto err_out_driver_exit;
-
-			cpufreq_debug_enable_ratelimit();
-			ret = 0;
-			goto err_out_driver_exit; /* call driver->exit() */
+				cpufreq_cpu_put(managed_policy);
+			/*
+			 * Success. We only needed to be added to the mask.
+			 * Call driver->exit() because only the cpu parent of
+			 * the kobj needed to call init().
+			 */
+			goto out_driver_exit; /* call driver->exit() */
 		}
 	}
 #endif
@@ -892,29 +903,31 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 	ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq, &sys_dev->kobj,
 				   "cpufreq");
 	if (ret)
-		goto err_out_driver_exit;
+		goto out_driver_exit;
 
 	/* set up files for this cpu device */
 	drv_attr = cpufreq_driver->attr;
 	while ((drv_attr) && (*drv_attr)) {
 		ret = sysfs_create_file(&policy->kobj, &((*drv_attr)->attr));
 		if (ret)
-			goto err_out_driver_exit;
+			goto err_out_kobj_put;
 		drv_attr++;
 	}
 	if (cpufreq_driver->get) {
 		ret = sysfs_create_file(&policy->kobj, &cpuinfo_cur_freq.attr);
 		if (ret)
-			goto err_out_driver_exit;
+			goto err_out_kobj_put;
 	}
 	if (cpufreq_driver->target) {
 		ret = sysfs_create_file(&policy->kobj, &scaling_cur_freq.attr);
 		if (ret)
-			goto err_out_driver_exit;
+			goto err_out_kobj_put;
 	}
 
 	spin_lock_irqsave(&cpufreq_driver_lock, flags);
 	for_each_cpu(j, policy->cpus) {
+		if (!cpu_online(j))
+			continue;
 		per_cpu(cpufreq_cpu_data, j) = policy;
 		per_cpu(policy_cpu, j) = policy->cpu;
 	}
@@ -922,18 +935,22 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
 
 	/* symlink affected CPUs */
 	for_each_cpu(j, policy->cpus) {
+		struct cpufreq_policy *managed_policy;
+
 		if (j == cpu)
 			continue;
 		if (!cpu_online(j))
 			continue;
 
 		dprintk("CPU %u already managed, adding link\n", j);
-		cpufreq_cpu_get(cpu);
+		managed_policy = cpufreq_cpu_get(cpu);
 		cpu_sys_dev = get_cpu_sysdev(j);
 		ret = sysfs_create_link(&cpu_sys_dev->kobj, &policy->kobj,
 					"cpufreq");
-		if (ret)
+		if (ret) {
+			cpufreq_cpu_put(managed_policy);
 			goto err_out_unregister;
+		}
 	}
 
 	policy->governor = NULL; /* to assure that the starting sequence is
@@ -965,17 +982,20 @@ err_out_unregister:
 		per_cpu(cpufreq_cpu_data, j) = NULL;
 	spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
+err_out_kobj_put:
 	kobject_put(&policy->kobj);
 	wait_for_completion(&policy->kobj_unregister);
 
-err_out_driver_exit:
+out_driver_exit:
 	if (cpufreq_driver->exit)
 		cpufreq_driver->exit(policy);
 
-err_out:
+err_unlock_policy:
 	unlock_policy_rwsem_write(cpu);
+err_free_cpumask:
+	free_cpumask_var(policy->cpus);
+err_free_policy:
 	kfree(policy);
-
 nomem_out:
 	module_put(cpufreq_driver->owner);
 module_out:
@@ -1070,8 +1090,6 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
 	spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
 #endif
 
-	unlock_policy_rwsem_write(cpu);
-
 	if (cpufreq_driver->target)
 		__cpufreq_governor(data, CPUFREQ_GOV_STOP);
 
@@ -1088,6 +1106,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
 	if (cpufreq_driver->exit)
 		cpufreq_driver->exit(data);
 
+	unlock_policy_rwsem_write(cpu);
+
 	free_cpumask_var(data->related_cpus);
 	free_cpumask_var(data->cpus);
 	kfree(data);
@@ -1228,13 +1248,22 @@ EXPORT_SYMBOL(cpufreq_get);
 
 static int cpufreq_suspend(struct sys_device *sysdev, pm_message_t pmsg)
 {
-	int cpu = sysdev->id;
 	int ret = 0;
+
+#ifdef __powerpc__
+	int cpu = sysdev->id;
 	unsigned int cur_freq = 0;
 	struct cpufreq_policy *cpu_policy;
 
 	dprintk("suspending cpu %u\n", cpu);
 
+	/*
+	 * This whole bogosity is here because Powerbooks are made of fail.
+	 * No sane platform should need any of the code below to be run.
+	 * (it's entirely the wrong thing to do, as driver->get may
+	 *  reenable interrupts on some architectures).
+	 */
+
 	if (!cpu_online(cpu))
 		return 0;
 
@@ -1293,6 +1322,7 @@ static int cpufreq_suspend(struct sys_device *sysdev, pm_message_t pmsg)
 
 out:
 	cpufreq_cpu_put(cpu_policy);
+#endif	/* __powerpc__ */
 	return ret;
 }
 
@@ -1306,12 +1336,18 @@ out:
  */
 static int cpufreq_resume(struct sys_device *sysdev)
 {
-	int cpu = sysdev->id;
 	int ret = 0;
+
+#ifdef __powerpc__
+	int cpu = sysdev->id;
 	struct cpufreq_policy *cpu_policy;
 
 	dprintk("resuming cpu %u\n", cpu);
 
+	/* As with the ->suspend method, all the code below is
+	 * only necessary because Powerbooks suck.
+	 * See commit 42d4dc3f4e1e for jokes. */
+
 	if (!cpu_online(cpu))
 		return 0;
 
@@ -1375,6 +1411,7 @@ out:
 	schedule_work(&cpu_policy->update);
 fail:
 	cpufreq_cpu_put(cpu_policy);
+#endif	/* __powerpc__ */
 	return ret;
 }
 
diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index 7a74d175287..bdea7e2f94b 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -42,27 +42,12 @@
  * this governor will not work.
  * All times here are in uS.
  */
-static unsigned int def_sampling_rate;
 #define MIN_SAMPLING_RATE_RATIO			(2)
-/* for correct statistics, we need at least 10 ticks between each measure */
-#define MIN_STAT_SAMPLING_RATE 			\
-			(MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
-#define MIN_SAMPLING_RATE			\
-			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
-/* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon
- * Define the minimal settable sampling rate to the greater of:
- *   - "HW transition latency" * 100 (same as default sampling / 10)
- *   - MIN_STAT_SAMPLING_RATE
- * To avoid that userspace shoots itself.
-*/
-static unsigned int minimum_sampling_rate(void)
-{
-	return max(def_sampling_rate / 10, MIN_STAT_SAMPLING_RATE);
-}
 
-/* This will also vanish soon with removing sampling_rate_max */
-#define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
+static unsigned int min_sampling_rate;
+
 #define LATENCY_MULTIPLIER			(1000)
+#define MIN_LATENCY_MULTIPLIER			(100)
 #define DEF_SAMPLING_DOWN_FACTOR		(1)
 #define MAX_SAMPLING_DOWN_FACTOR		(10)
 #define TRANSITION_LATENCY_LIMIT		(10 * 1000 * 1000)
@@ -79,21 +64,20 @@ struct cpu_dbs_info_s {
 	unsigned int requested_freq;
 	int cpu;
 	unsigned int enable:1;
+	/*
+	 * percpu mutex that serializes governor limit change with
+	 * do_dbs_timer invocation. We do not want do_dbs_timer to run
+	 * when user is changing the governor or limits.
+	 */
+	struct mutex timer_mutex;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
 
 static unsigned int dbs_enable;	/* number of CPUs using this policy */
 
 /*
- * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
- * lock and dbs_mutex. cpu_hotplug lock should always be held before
- * dbs_mutex. If any function that can potentially take cpu_hotplug lock
- * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
- * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
- * is recursive for the same process. -Venki
- * DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
- * would deadlock with cancel_delayed_work_sync(), which is needed for proper
- * raceless workqueue teardown.
+ * dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
+ * different CPUs. It protects dbs_enable in governor start/stop.
  */
 static DEFINE_MUTEX(dbs_mutex);
 
@@ -182,27 +166,14 @@ static struct notifier_block dbs_cpufreq_notifier_block = {
 /************************** sysfs interface ************************/
 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 {
-	static int print_once;
-
-	if (!print_once) {
-		printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
-		       "sysfs file is deprecated - used by: %s\n",
-		       current->comm);
-		print_once = 1;
-	}
-	return sprintf(buf, "%u\n", MAX_SAMPLING_RATE);
+	printk_once(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
+		    "sysfs file is deprecated - used by: %s\n", current->comm);
+	return sprintf(buf, "%u\n", -1U);
 }
 
 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 {
-	static int print_once;
-
-	if (!print_once) {
-		printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "
-		       "sysfs file is deprecated - used by: %s\n", current->comm);
-		print_once = 1;
-	}
-	return sprintf(buf, "%u\n", MIN_SAMPLING_RATE);
+	return sprintf(buf, "%u\n", min_sampling_rate);
 }
 
 #define define_one_ro(_name)		\
@@ -254,7 +225,7 @@ static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 		return -EINVAL;
 
 	mutex_lock(&dbs_mutex);
-	dbs_tuners_ins.sampling_rate = max(input, minimum_sampling_rate());
+	dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 	mutex_unlock(&dbs_mutex);
 
 	return count;
@@ -516,18 +487,12 @@ static void do_dbs_timer(struct work_struct *work)
 
 	delay -= jiffies % delay;
 
-	if (lock_policy_rwsem_write(cpu) < 0)
-		return;
-
-	if (!dbs_info->enable) {
-		unlock_policy_rwsem_write(cpu);
-		return;
-	}
+	mutex_lock(&dbs_info->timer_mutex);
 
 	dbs_check_cpu(dbs_info);
 
 	queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
-	unlock_policy_rwsem_write(cpu);
+	mutex_unlock(&dbs_info->timer_mutex);
 }
 
 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -563,9 +528,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		if ((!cpu_online(cpu)) || (!policy->cur))
 			return -EINVAL;
 
-		if (this_dbs_info->enable) /* Already enabled */
-			break;
-
 		mutex_lock(&dbs_mutex);
 
 		rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
@@ -589,6 +551,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		this_dbs_info->down_skip = 0;
 		this_dbs_info->requested_freq = policy->cur;
 
+		mutex_init(&this_dbs_info->timer_mutex);
 		dbs_enable++;
 		/*
 		 * Start the timerschedule work, when this governor
@@ -601,27 +564,36 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 			if (latency == 0)
 				latency = 1;
 
-			def_sampling_rate =
-				max(latency * LATENCY_MULTIPLIER,
-				    MIN_STAT_SAMPLING_RATE);
-
-			dbs_tuners_ins.sampling_rate = def_sampling_rate;
+			/*
+			 * conservative does not implement micro like ondemand
+			 * governor, thus we are bound to jiffes/HZ
+			 */
+			min_sampling_rate =
+				MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
+			/* Bring kernel and HW constraints together */
+			min_sampling_rate = max(min_sampling_rate,
+					MIN_LATENCY_MULTIPLIER * latency);
+			dbs_tuners_ins.sampling_rate =
+				max(min_sampling_rate,
+				    latency * LATENCY_MULTIPLIER);
 
 			cpufreq_register_notifier(
 					&dbs_cpufreq_notifier_block,
 					CPUFREQ_TRANSITION_NOTIFIER);
 		}
-		dbs_timer_init(this_dbs_info);
-
 		mutex_unlock(&dbs_mutex);
 
+		dbs_timer_init(this_dbs_info);
+
 		break;
 
 	case CPUFREQ_GOV_STOP:
-		mutex_lock(&dbs_mutex);
 		dbs_timer_exit(this_dbs_info);
+
+		mutex_lock(&dbs_mutex);
 		sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 		dbs_enable--;
+		mutex_destroy(&this_dbs_info->timer_mutex);
 
 		/*
 		 * Stop the timerschedule work, when this governor
@@ -637,7 +609,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		break;
 
 	case CPUFREQ_GOV_LIMITS:
-		mutex_lock(&dbs_mutex);
+		mutex_lock(&this_dbs_info->timer_mutex);
 		if (policy->max < this_dbs_info->cur_policy->cur)
 			__cpufreq_driver_target(
 					this_dbs_info->cur_policy,
@@ -646,7 +618,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 			__cpufreq_driver_target(
 					this_dbs_info->cur_policy,
 					policy->min, CPUFREQ_RELATION_L);
-		mutex_unlock(&dbs_mutex);
+		mutex_unlock(&this_dbs_info->timer_mutex);
 
 		break;
 	}
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index e741c339df7..d6ba14276bb 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -32,6 +32,7 @@
 #define DEF_FREQUENCY_UP_THRESHOLD		(80)
 #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL	(3)
 #define MICRO_FREQUENCY_UP_THRESHOLD		(95)
+#define MICRO_FREQUENCY_MIN_SAMPLE_RATE		(10000)
 #define MIN_FREQUENCY_UP_THRESHOLD		(11)
 #define MAX_FREQUENCY_UP_THRESHOLD		(100)
 
@@ -45,27 +46,12 @@
  * this governor will not work.
  * All times here are in uS.
  */
-static unsigned int def_sampling_rate;
 #define MIN_SAMPLING_RATE_RATIO			(2)
-/* for correct statistics, we need at least 10 ticks between each measure */
-#define MIN_STAT_SAMPLING_RATE 			\
-			(MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
-#define MIN_SAMPLING_RATE			\
-			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
-/* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon
- * Define the minimal settable sampling rate to the greater of:
- *   - "HW transition latency" * 100 (same as default sampling / 10)
- *   - MIN_STAT_SAMPLING_RATE
- * To avoid that userspace shoots itself.
-*/
-static unsigned int minimum_sampling_rate(void)
-{
-	return max(def_sampling_rate / 10, MIN_STAT_SAMPLING_RATE);
-}
 
-/* This will also vanish soon with removing sampling_rate_max */
-#define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
+static unsigned int min_sampling_rate;
+
 #define LATENCY_MULTIPLIER			(1000)
+#define MIN_LATENCY_MULTIPLIER			(100)
 #define TRANSITION_LATENCY_LIMIT		(10 * 1000 * 1000)
 
 static void do_dbs_timer(struct work_struct *work);
@@ -84,23 +70,21 @@ struct cpu_dbs_info_s {
 	unsigned int freq_lo_jiffies;
 	unsigned int freq_hi_jiffies;
 	int cpu;
-	unsigned int enable:1,
-		sample_type:1;
+	unsigned int sample_type:1;
+	/*
+	 * percpu mutex that serializes governor limit change with
+	 * do_dbs_timer invocation. We do not want do_dbs_timer to run
+	 * when user is changing the governor or limits.
+	 */
+	struct mutex timer_mutex;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
 
 static unsigned int dbs_enable;	/* number of CPUs using this policy */
 
 /*
- * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
- * lock and dbs_mutex. cpu_hotplug lock should always be held before
- * dbs_mutex. If any function that can potentially take cpu_hotplug lock
- * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
- * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
- * is recursive for the same process. -Venki
- * DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
- * would deadlock with cancel_delayed_work_sync(), which is needed for proper
- * raceless workqueue teardown.
+ * dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
+ * different CPUs. It protects dbs_enable in governor start/stop.
  */
 static DEFINE_MUTEX(dbs_mutex);
 
@@ -206,41 +190,32 @@ static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
 	return freq_hi;
 }
 
+static void ondemand_powersave_bias_init_cpu(int cpu)
+{
+	struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+	dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
+	dbs_info->freq_lo = 0;
+}
+
 static void ondemand_powersave_bias_init(void)
 {
 	int i;
 	for_each_online_cpu(i) {
-		struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
-		dbs_info->freq_table = cpufreq_frequency_get_table(i);
-		dbs_info->freq_lo = 0;
+		ondemand_powersave_bias_init_cpu(i);
 	}
 }
 
 /************************** sysfs interface ************************/
 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 {
-	static int print_once;
-
-	if (!print_once) {
-		printk(KERN_INFO "CPUFREQ: ondemand sampling_rate_max "
-		       "sysfs file is deprecated - used by: %s\n",
-		       current->comm);
-		print_once = 1;
-	}
-	return sprintf(buf, "%u\n", MAX_SAMPLING_RATE);
+	printk_once(KERN_INFO "CPUFREQ: ondemand sampling_rate_max "
+	       "sysfs file is deprecated - used by: %s\n", current->comm);
+	return sprintf(buf, "%u\n", -1U);
 }
 
 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 {
-	static int print_once;
-
-	if (!print_once) {
-		printk(KERN_INFO "CPUFREQ: ondemand sampling_rate_min "
-		       "sysfs file is deprecated - used by: %s\n",
-		       current->comm);
-		print_once = 1;
-	}
-	return sprintf(buf, "%u\n", MIN_SAMPLING_RATE);
+	return sprintf(buf, "%u\n", min_sampling_rate);
 }
 
 #define define_one_ro(_name)		\
@@ -268,13 +243,11 @@ static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 	unsigned int input;
 	int ret;
 	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
 
 	mutex_lock(&dbs_mutex);
-	if (ret != 1) {
-		mutex_unlock(&dbs_mutex);
-		return -EINVAL;
-	}
-	dbs_tuners_ins.sampling_rate = max(input, minimum_sampling_rate());
+	dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
 	mutex_unlock(&dbs_mutex);
 
 	return count;
@@ -287,13 +260,12 @@ static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 	int ret;
 	ret = sscanf(buf, "%u", &input);
 
-	mutex_lock(&dbs_mutex);
 	if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 			input < MIN_FREQUENCY_UP_THRESHOLD) {
-		mutex_unlock(&dbs_mutex);
 		return -EINVAL;
 	}
 
+	mutex_lock(&dbs_mutex);
 	dbs_tuners_ins.up_threshold = input;
 	mutex_unlock(&dbs_mutex);
 
@@ -391,9 +363,6 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 	struct cpufreq_policy *policy;
 	unsigned int j;
 
-	if (!this_dbs_info->enable)
-		return;
-
 	this_dbs_info->freq_lo = 0;
 	policy = this_dbs_info->cur_policy;
 
@@ -521,14 +490,7 @@ static void do_dbs_timer(struct work_struct *work)
 	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 
 	delay -= jiffies % delay;
-
-	if (lock_policy_rwsem_write(cpu) < 0)
-		return;
-
-	if (!dbs_info->enable) {
-		unlock_policy_rwsem_write(cpu);
-		return;
-	}
+	mutex_lock(&dbs_info->timer_mutex);
 
 	/* Common NORMAL_SAMPLE setup */
 	dbs_info->sample_type = DBS_NORMAL_SAMPLE;
@@ -545,7 +507,7 @@ static void do_dbs_timer(struct work_struct *work)
 			dbs_info->freq_lo, CPUFREQ_RELATION_H);
 	}
 	queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
-	unlock_policy_rwsem_write(cpu);
+	mutex_unlock(&dbs_info->timer_mutex);
 }
 
 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -554,8 +516,6 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 	delay -= jiffies % delay;
 
-	dbs_info->enable = 1;
-	ondemand_powersave_bias_init();
 	dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 	INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
 	queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
@@ -564,7 +524,6 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 
 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 {
-	dbs_info->enable = 0;
 	cancel_delayed_work_sync(&dbs_info->work);
 }
 
@@ -583,19 +542,15 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		if ((!cpu_online(cpu)) || (!policy->cur))
 			return -EINVAL;
 
-		if (this_dbs_info->enable) /* Already enabled */
-			break;
-
 		mutex_lock(&dbs_mutex);
-		dbs_enable++;
 
 		rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 		if (rc) {
-			dbs_enable--;
 			mutex_unlock(&dbs_mutex);
 			return rc;
 		}
 
+		dbs_enable++;
 		for_each_cpu(j, policy->cpus) {
 			struct cpu_dbs_info_s *j_dbs_info;
 			j_dbs_info = &per_cpu(cpu_dbs_info, j);
@@ -609,6 +564,8 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 			}
 		}
 		this_dbs_info->cpu = cpu;
+		ondemand_powersave_bias_init_cpu(cpu);
+		mutex_init(&this_dbs_info->timer_mutex);
 		/*
 		 * Start the timerschedule work, when this governor
 		 * is used for first time
@@ -619,36 +576,38 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 			latency = policy->cpuinfo.transition_latency / 1000;
 			if (latency == 0)
 				latency = 1;
-
-			def_sampling_rate =
-				max(latency * LATENCY_MULTIPLIER,
-				    MIN_STAT_SAMPLING_RATE);
-
-			dbs_tuners_ins.sampling_rate = def_sampling_rate;
+			/* Bring kernel and HW constraints together */
+			min_sampling_rate = max(min_sampling_rate,
+					MIN_LATENCY_MULTIPLIER * latency);
+			dbs_tuners_ins.sampling_rate =
+				max(min_sampling_rate,
+				    latency * LATENCY_MULTIPLIER);
 		}
-		dbs_timer_init(this_dbs_info);
-
 		mutex_unlock(&dbs_mutex);
+
+		dbs_timer_init(this_dbs_info);
 		break;
 
 	case CPUFREQ_GOV_STOP:
-		mutex_lock(&dbs_mutex);
 		dbs_timer_exit(this_dbs_info);
+
+		mutex_lock(&dbs_mutex);
 		sysfs_remove_group(&policy->kobj, &dbs_attr_group);
+		mutex_destroy(&this_dbs_info->timer_mutex);
 		dbs_enable--;
 		mutex_unlock(&dbs_mutex);
 
 		break;
 
 	case CPUFREQ_GOV_LIMITS:
-		mutex_lock(&dbs_mutex);
+		mutex_lock(&this_dbs_info->timer_mutex);
 		if (policy->max < this_dbs_info->cur_policy->cur)
 			__cpufreq_driver_target(this_dbs_info->cur_policy,
 				policy->max, CPUFREQ_RELATION_H);
 		else if (policy->min > this_dbs_info->cur_policy->cur)
 			__cpufreq_driver_target(this_dbs_info->cur_policy,
 				policy->min, CPUFREQ_RELATION_L);
-		mutex_unlock(&dbs_mutex);
+		mutex_unlock(&this_dbs_info->timer_mutex);
 		break;
 	}
 	return 0;
@@ -678,6 +637,16 @@ static int __init cpufreq_gov_dbs_init(void)
 		dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
 		dbs_tuners_ins.down_differential =
 					MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
+		/*
+		 * In no_hz/micro accounting case we set the minimum frequency
+		 * not depending on HZ, but fixed (very low). The deferred
+		 * timer might skip some samples if idle/sleeping as needed.
+		*/
+		min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
+	} else {
+		/* For correct statistics, we need 10 ticks for each measure */
+		min_sampling_rate =
+			MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 	}
 
 	kondemand_wq = create_workqueue("kondemand");