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cpufreq: Simplify cpufreq_add_dev()
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Currently cpufreq_add_dev() firsts allocates policy, calls
driver->init() and then checks if this CPU is already managed or not.
And if it is already managed, its policy is freed.

We can save all this if we somehow know that CPU is managed or not in
advance.  policy->related_cpus contains the list of all valid sibling
CPUs of policy->cpu. We can check this to see if the current CPU is
already managed.

From now on, platforms don't really need to set related_cpus from
their init() routines, as the same work is done by core too.

If a platform driver needs to set the related_cpus mask with some
additional CPUs, other than CPUs present in policy->cpus, they are
free to do it, though, as we don't override anything.

[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Viresh Kumar authored and Rafael J. Wysocki committed Feb 1, 2013
1 parent b26f720 commit fcf8058
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Showing 2 changed files with 58 additions and 101 deletions.
158 changes: 58 additions & 100 deletions drivers/cpufreq/cpufreq.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -552,8 +552,6 @@ static ssize_t show_cpus(const struct cpumask *mask, char *buf)
*/
static ssize_t show_related_cpus(struct cpufreq_policy *policy, char *buf)
{
if (cpumask_empty(policy->related_cpus))
return show_cpus(policy->cpus, buf);
return show_cpus(policy->related_cpus, buf);
}

Expand Down Expand Up @@ -709,92 +707,6 @@ static struct kobj_type ktype_cpufreq = {
.release = cpufreq_sysfs_release,
};

/*
* Returns:
* Negative: Failure
* 0: Success
* Positive: When we have a managed CPU and the sysfs got symlinked
*/
static int cpufreq_add_dev_policy(unsigned int cpu,
struct cpufreq_policy *policy,
struct device *dev)
{
int ret = 0;
#ifdef CONFIG_SMP
unsigned long flags;
unsigned int j;
#ifdef CONFIG_HOTPLUG_CPU
struct cpufreq_governor *gov;

gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
if (gov) {
policy->governor = gov;
pr_debug("Restoring governor %s for cpu %d\n",
policy->governor->name, cpu);
}
#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);
if (unlikely(managed_policy)) {

/* Set proper policy_cpu */
unlock_policy_rwsem_write(cpu);
per_cpu(cpufreq_policy_cpu, cpu) = managed_policy->cpu;

if (lock_policy_rwsem_write(cpu) < 0) {
/* Should not go through policy unlock path */
if (cpufreq_driver->exit)
cpufreq_driver->exit(policy);
cpufreq_cpu_put(managed_policy);
return -EBUSY;
}

__cpufreq_governor(managed_policy, CPUFREQ_GOV_STOP);

spin_lock_irqsave(&cpufreq_driver_lock, flags);
cpumask_copy(managed_policy->cpus, policy->cpus);
per_cpu(cpufreq_cpu_data, cpu) = managed_policy;
spin_unlock_irqrestore(&cpufreq_driver_lock, flags);

__cpufreq_governor(managed_policy, CPUFREQ_GOV_START);
__cpufreq_governor(managed_policy, CPUFREQ_GOV_LIMITS);

pr_debug("CPU already managed, adding link\n");
ret = sysfs_create_link(&dev->kobj,
&managed_policy->kobj,
"cpufreq");
if (ret)
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().
*/
if (cpufreq_driver->exit)
cpufreq_driver->exit(policy);

if (!ret)
return 1;
else
return ret;
}
}
#endif
return ret;
}


/* symlink affected CPUs */
static int cpufreq_add_dev_symlink(unsigned int cpu,
struct cpufreq_policy *policy)
Expand Down Expand Up @@ -899,6 +811,42 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
return ret;
}

#ifdef CONFIG_HOTPLUG_CPU
static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
struct device *dev)
{
struct cpufreq_policy *policy;
int ret = 0;
unsigned long flags;

policy = cpufreq_cpu_get(sibling);
WARN_ON(!policy);

per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;

lock_policy_rwsem_write(cpu);

__cpufreq_governor(policy, CPUFREQ_GOV_STOP);

spin_lock_irqsave(&cpufreq_driver_lock, flags);
cpumask_set_cpu(cpu, policy->cpus);
per_cpu(cpufreq_cpu_data, cpu) = policy;
spin_unlock_irqrestore(&cpufreq_driver_lock, flags);

__cpufreq_governor(policy, CPUFREQ_GOV_START);
__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);

unlock_policy_rwsem_write(cpu);

ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
if (ret) {
cpufreq_cpu_put(policy);
return ret;
}

return 0;
}
#endif

/**
* cpufreq_add_dev - add a CPU device
Expand All @@ -911,12 +859,12 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
*/
static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
{
unsigned int cpu = dev->id;
int ret = 0, found = 0;
unsigned int j, cpu = dev->id;
int ret = -ENOMEM, found = 0;
struct cpufreq_policy *policy;
unsigned long flags;
unsigned int j;
#ifdef CONFIG_HOTPLUG_CPU
struct cpufreq_governor *gov;
int sibling;
#endif

Expand All @@ -933,14 +881,22 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
cpufreq_cpu_put(policy);
return 0;
}

#ifdef CONFIG_HOTPLUG_CPU
/* Check if this cpu was hot-unplugged earlier and has siblings */
for_each_online_cpu(sibling) {
struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
if (cp && cpumask_test_cpu(cpu, cp->related_cpus))
return cpufreq_add_policy_cpu(cpu, sibling, dev);
}
#endif
#endif

if (!try_module_get(cpufreq_driver->owner)) {
ret = -EINVAL;
goto module_out;
}

ret = -ENOMEM;
policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
if (!policy)
goto nomem_out;
Expand Down Expand Up @@ -985,6 +941,9 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
goto err_unlock_policy;
}

/* related cpus should atleast have policy->cpus */
cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);

/*
* affected cpus must always be the one, which are online. We aren't
* managing offline cpus here.
Expand All @@ -997,14 +956,14 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
CPUFREQ_START, policy);

ret = cpufreq_add_dev_policy(cpu, policy, dev);
if (ret) {
if (ret > 0)
/* This is a managed cpu, symlink created,
exit with 0 */
ret = 0;
goto err_unlock_policy;
#ifdef CONFIG_HOTPLUG_CPU
gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
if (gov) {
policy->governor = gov;
pr_debug("Restoring governor %s for cpu %d\n",
policy->governor->name, cpu);
}
#endif

ret = cpufreq_add_dev_interface(cpu, policy, dev);
if (ret)
Expand All @@ -1018,7 +977,6 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)

return 0;


err_out_unregister:
spin_lock_irqsave(&cpufreq_driver_lock, flags);
for_each_cpu(j, policy->cpus)
Expand Down
1 change: 0 additions & 1 deletion drivers/cpufreq/spear-cpufreq.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,6 @@ static int spear_cpufreq_init(struct cpufreq_policy *policy)
policy->cur = spear_cpufreq_get(0);

cpumask_copy(policy->cpus, topology_core_cpumask(policy->cpu));
cpumask_copy(policy->related_cpus, policy->cpus);

return 0;
}
Expand Down

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