cpufreq: Support for fast frequency switching
Modify the ACPI cpufreq driver to provide a method for switching CPU frequencies from interrupt context and update the cpufreq core to support that method if available. Introduce a new cpufreq driver callback, ->fast_switch, to be invoked for frequency switching from interrupt context by (future) governors supporting that feature via (new) helper function cpufreq_driver_fast_switch(). Add two new policy flags, fast_switch_possible, to be set by the cpufreq driver if fast frequency switching can be used for the given policy and fast_switch_enabled, to be set by the governor if it is going to use fast frequency switching for the given policy. Also add a helper for setting the latter. Since fast frequency switching is inherently incompatible with cpufreq transition notifiers, make it possible to set the fast_switch_enabled only if there are no transition notifiers already registered and make the registration of new transition notifiers fail if fast_switch_enabled is set for at least one policy. Implement the ->fast_switch callback in the ACPI cpufreq driver and make it set fast_switch_possible during policy initialization as appropriate. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
This commit is contained in:
Rafael J. Wysocki
Родитель
379480d825
Коммит
b7898fda5b
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@ -458,6 +458,43 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
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return result;
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}
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unsigned int acpi_cpufreq_fast_switch(struct cpufreq_policy *policy,
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unsigned int target_freq)
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{
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struct acpi_cpufreq_data *data = policy->driver_data;
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struct acpi_processor_performance *perf;
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struct cpufreq_frequency_table *entry;
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unsigned int next_perf_state, next_freq, freq;
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/*
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* Find the closest frequency above target_freq.
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*
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* The table is sorted in the reverse order with respect to the
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* frequency and all of the entries are valid (see the initialization).
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*/
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entry = data->freq_table;
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do {
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entry++;
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freq = entry->frequency;
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} while (freq >= target_freq && freq != CPUFREQ_TABLE_END);
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entry--;
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next_freq = entry->frequency;
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next_perf_state = entry->driver_data;
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perf = to_perf_data(data);
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if (perf->state == next_perf_state) {
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if (unlikely(data->resume))
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data->resume = 0;
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else
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return next_freq;
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}
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data->cpu_freq_write(&perf->control_register,
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perf->states[next_perf_state].control);
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perf->state = next_perf_state;
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return next_freq;
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}
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static unsigned long
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acpi_cpufreq_guess_freq(struct acpi_cpufreq_data *data, unsigned int cpu)
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{
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@ -821,6 +858,9 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
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*/
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data->resume = 1;
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policy->fast_switch_possible = !acpi_pstate_strict &&
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!(policy_is_shared(policy) && policy->shared_type != CPUFREQ_SHARED_TYPE_ANY);
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return result;
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err_freqfree:
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@ -843,6 +883,7 @@ static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
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pr_debug("acpi_cpufreq_cpu_exit\n");
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if (data) {
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policy->fast_switch_possible = false;
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policy->driver_data = NULL;
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acpi_processor_unregister_performance(data->acpi_perf_cpu);
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free_cpumask_var(data->freqdomain_cpus);
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@ -876,6 +917,7 @@ static struct freq_attr *acpi_cpufreq_attr[] = {
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static struct cpufreq_driver acpi_cpufreq_driver = {
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.verify = cpufreq_generic_frequency_table_verify,
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.target_index = acpi_cpufreq_target,
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.fast_switch = acpi_cpufreq_fast_switch,
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.bios_limit = acpi_processor_get_bios_limit,
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.init = acpi_cpufreq_cpu_init,
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.exit = acpi_cpufreq_cpu_exit,
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@ -77,6 +77,7 @@ static inline bool has_target(void)
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static int cpufreq_governor(struct cpufreq_policy *policy, unsigned int event);
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static unsigned int __cpufreq_get(struct cpufreq_policy *policy);
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static int cpufreq_start_governor(struct cpufreq_policy *policy);
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static int cpufreq_exit_governor(struct cpufreq_policy *policy);
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/**
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* Two notifier lists: the "policy" list is involved in the
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@ -429,6 +430,68 @@ void cpufreq_freq_transition_end(struct cpufreq_policy *policy,
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}
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EXPORT_SYMBOL_GPL(cpufreq_freq_transition_end);
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/*
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* Fast frequency switching status count. Positive means "enabled", negative
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* means "disabled" and 0 means "not decided yet".
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*/
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static int cpufreq_fast_switch_count;
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static DEFINE_MUTEX(cpufreq_fast_switch_lock);
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static void cpufreq_list_transition_notifiers(void)
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{
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struct notifier_block *nb;
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pr_info("Registered transition notifiers:\n");
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mutex_lock(&cpufreq_transition_notifier_list.mutex);
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for (nb = cpufreq_transition_notifier_list.head; nb; nb = nb->next)
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pr_info("%pF\n", nb->notifier_call);
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mutex_unlock(&cpufreq_transition_notifier_list.mutex);
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}
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/**
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* cpufreq_enable_fast_switch - Enable fast frequency switching for policy.
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* @policy: cpufreq policy to enable fast frequency switching for.
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*
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* Try to enable fast frequency switching for @policy.
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*
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* The attempt will fail if there is at least one transition notifier registered
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* at this point, as fast frequency switching is quite fundamentally at odds
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* with transition notifiers. Thus if successful, it will make registration of
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* transition notifiers fail going forward.
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*/
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void cpufreq_enable_fast_switch(struct cpufreq_policy *policy)
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{
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lockdep_assert_held(&policy->rwsem);
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if (!policy->fast_switch_possible)
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return;
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mutex_lock(&cpufreq_fast_switch_lock);
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if (cpufreq_fast_switch_count >= 0) {
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cpufreq_fast_switch_count++;
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policy->fast_switch_enabled = true;
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} else {
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pr_warn("CPU%u: Fast frequency switching not enabled\n",
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policy->cpu);
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cpufreq_list_transition_notifiers();
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}
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mutex_unlock(&cpufreq_fast_switch_lock);
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}
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EXPORT_SYMBOL_GPL(cpufreq_enable_fast_switch);
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static void cpufreq_disable_fast_switch(struct cpufreq_policy *policy)
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{
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mutex_lock(&cpufreq_fast_switch_lock);
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if (policy->fast_switch_enabled) {
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policy->fast_switch_enabled = false;
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if (!WARN_ON(cpufreq_fast_switch_count <= 0))
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cpufreq_fast_switch_count--;
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}
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mutex_unlock(&cpufreq_fast_switch_lock);
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}
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/*********************************************************************
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* SYSFS INTERFACE *
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@ -1319,7 +1382,7 @@ static void cpufreq_offline(unsigned int cpu)
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/* If cpu is last user of policy, free policy */
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if (has_target()) {
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ret = cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);
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ret = cpufreq_exit_governor(policy);
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if (ret)
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pr_err("%s: Failed to exit governor\n", __func__);
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}
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@ -1447,8 +1510,12 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy)
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ret_freq = cpufreq_driver->get(policy->cpu);
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/* Updating inactive policies is invalid, so avoid doing that. */
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if (unlikely(policy_is_inactive(policy)))
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/*
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* Updating inactive policies is invalid, so avoid doing that. Also
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* if fast frequency switching is used with the given policy, the check
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* against policy->cur is pointless, so skip it in that case too.
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*/
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if (unlikely(policy_is_inactive(policy)) || policy->fast_switch_enabled)
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return ret_freq;
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if (ret_freq && policy->cur &&
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@ -1672,8 +1739,18 @@ int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list)
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switch (list) {
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case CPUFREQ_TRANSITION_NOTIFIER:
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mutex_lock(&cpufreq_fast_switch_lock);
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if (cpufreq_fast_switch_count > 0) {
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mutex_unlock(&cpufreq_fast_switch_lock);
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return -EBUSY;
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}
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ret = srcu_notifier_chain_register(
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&cpufreq_transition_notifier_list, nb);
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if (!ret)
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cpufreq_fast_switch_count--;
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mutex_unlock(&cpufreq_fast_switch_lock);
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break;
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case CPUFREQ_POLICY_NOTIFIER:
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ret = blocking_notifier_chain_register(
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@ -1706,8 +1783,14 @@ int cpufreq_unregister_notifier(struct notifier_block *nb, unsigned int list)
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switch (list) {
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case CPUFREQ_TRANSITION_NOTIFIER:
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mutex_lock(&cpufreq_fast_switch_lock);
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ret = srcu_notifier_chain_unregister(
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&cpufreq_transition_notifier_list, nb);
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if (!ret && !WARN_ON(cpufreq_fast_switch_count >= 0))
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cpufreq_fast_switch_count++;
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mutex_unlock(&cpufreq_fast_switch_lock);
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break;
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case CPUFREQ_POLICY_NOTIFIER:
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ret = blocking_notifier_chain_unregister(
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@ -1726,6 +1809,37 @@ EXPORT_SYMBOL(cpufreq_unregister_notifier);
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* GOVERNORS *
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*********************************************************************/
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/**
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* cpufreq_driver_fast_switch - Carry out a fast CPU frequency switch.
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* @policy: cpufreq policy to switch the frequency for.
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* @target_freq: New frequency to set (may be approximate).
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*
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* Carry out a fast frequency switch without sleeping.
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*
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* The driver's ->fast_switch() callback invoked by this function must be
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* suitable for being called from within RCU-sched read-side critical sections
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* and it is expected to select the minimum available frequency greater than or
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* equal to @target_freq (CPUFREQ_RELATION_L).
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*
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* This function must not be called if policy->fast_switch_enabled is unset.
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*
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* Governors calling this function must guarantee that it will never be invoked
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* twice in parallel for the same policy and that it will never be called in
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* parallel with either ->target() or ->target_index() for the same policy.
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*
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* If CPUFREQ_ENTRY_INVALID is returned by the driver's ->fast_switch()
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* callback to indicate an error condition, the hardware configuration must be
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* preserved.
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*/
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unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
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unsigned int target_freq)
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{
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clamp_val(target_freq, policy->min, policy->max);
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return cpufreq_driver->fast_switch(policy, target_freq);
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}
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EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch);
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/* Must set freqs->new to intermediate frequency */
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static int __target_intermediate(struct cpufreq_policy *policy,
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struct cpufreq_freqs *freqs, int index)
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@ -1946,6 +2060,12 @@ static int cpufreq_start_governor(struct cpufreq_policy *policy)
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return ret ? ret : cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
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}
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static int cpufreq_exit_governor(struct cpufreq_policy *policy)
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{
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cpufreq_disable_fast_switch(policy);
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return cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);
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}
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int cpufreq_register_governor(struct cpufreq_governor *governor)
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{
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int err;
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@ -2101,7 +2221,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
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return ret;
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}
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ret = cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);
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ret = cpufreq_exit_governor(policy);
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if (ret) {
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pr_err("%s: Failed to Exit Governor: %s (%d)\n",
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__func__, old_gov->name, ret);
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@ -2118,7 +2238,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
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pr_debug("cpufreq: governor change\n");
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return 0;
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}
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cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);
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cpufreq_exit_governor(policy);
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}
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/* new governor failed, so re-start old one */
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@ -102,6 +102,17 @@ struct cpufreq_policy {
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*/
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struct rw_semaphore rwsem;
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/*
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* Fast switch flags:
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* - fast_switch_possible should be set by the driver if it can
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* guarantee that frequency can be changed on any CPU sharing the
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* policy and that the change will affect all of the policy CPUs then.
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* - fast_switch_enabled is to be set by governors that support fast
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* freqnency switching with the help of cpufreq_enable_fast_switch().
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*/
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bool fast_switch_possible;
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bool fast_switch_enabled;
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/* Synchronization for frequency transitions */
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bool transition_ongoing; /* Tracks transition status */
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spinlock_t transition_lock;
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@ -156,6 +167,7 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu);
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int cpufreq_update_policy(unsigned int cpu);
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bool have_governor_per_policy(void);
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struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
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void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
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#else
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static inline unsigned int cpufreq_get(unsigned int cpu)
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{
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@ -236,6 +248,8 @@ struct cpufreq_driver {
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unsigned int relation); /* Deprecated */
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int (*target_index)(struct cpufreq_policy *policy,
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unsigned int index);
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unsigned int (*fast_switch)(struct cpufreq_policy *policy,
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unsigned int target_freq);
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/*
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* Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION
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* unset.
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@ -464,6 +478,8 @@ struct cpufreq_governor {
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};
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/* Pass a target to the cpufreq driver */
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unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
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unsigned int target_freq);
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int cpufreq_driver_target(struct cpufreq_policy *policy,
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unsigned int target_freq,
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unsigned int relation);
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