aboutsummaryrefslogtreecommitdiff
path: root/drivers/cpufreq/cpufreq_conservative.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/cpufreq/cpufreq_conservative.c')
-rw-r--r--drivers/cpufreq/cpufreq_conservative.c104
1 files changed, 38 insertions, 66 deletions
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;
}