aboutsummaryrefslogtreecommitdiff
path: root/drivers/cpufreq/acpi-cpufreq.c
diff options
context:
space:
mode:
authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-03-30 03:47:49 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-04-02 01:09:03 +0200
commitb7898fda5bc7e786e76ce24fbd2ec993b08ec518 (patch)
tree2bf721763c79a7fe0eca25349a549c52ba6ce483 /drivers/cpufreq/acpi-cpufreq.c
parent379480d8258056bfdbaa65e4d3f024bb5b34b52b (diff)
downloadleg-kernel-b7898fda5bc7e786e76ce24fbd2ec993b08ec518.tar.gz
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>
Diffstat (limited to 'drivers/cpufreq/acpi-cpufreq.c')
-rw-r--r--drivers/cpufreq/acpi-cpufreq.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index fb5712141040..7f38fb55f223 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -458,6 +458,43 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
return result;
}
+unsigned int acpi_cpufreq_fast_switch(struct cpufreq_policy *policy,
+ unsigned int target_freq)
+{
+ struct acpi_cpufreq_data *data = policy->driver_data;
+ struct acpi_processor_performance *perf;
+ struct cpufreq_frequency_table *entry;
+ unsigned int next_perf_state, next_freq, freq;
+
+ /*
+ * Find the closest frequency above target_freq.
+ *
+ * The table is sorted in the reverse order with respect to the
+ * frequency and all of the entries are valid (see the initialization).
+ */
+ entry = data->freq_table;
+ do {
+ entry++;
+ freq = entry->frequency;
+ } while (freq >= target_freq && freq != CPUFREQ_TABLE_END);
+ entry--;
+ next_freq = entry->frequency;
+ next_perf_state = entry->driver_data;
+
+ perf = to_perf_data(data);
+ if (perf->state == next_perf_state) {
+ if (unlikely(data->resume))
+ data->resume = 0;
+ else
+ return next_freq;
+ }
+
+ data->cpu_freq_write(&perf->control_register,
+ perf->states[next_perf_state].control);
+ perf->state = next_perf_state;
+ return next_freq;
+}
+
static unsigned long
acpi_cpufreq_guess_freq(struct acpi_cpufreq_data *data, unsigned int cpu)
{
@@ -821,6 +858,9 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
*/
data->resume = 1;
+ policy->fast_switch_possible = !acpi_pstate_strict &&
+ !(policy_is_shared(policy) && policy->shared_type != CPUFREQ_SHARED_TYPE_ANY);
+
return result;
err_freqfree:
@@ -843,6 +883,7 @@ static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
pr_debug("acpi_cpufreq_cpu_exit\n");
if (data) {
+ policy->fast_switch_possible = false;
policy->driver_data = NULL;
acpi_processor_unregister_performance(data->acpi_perf_cpu);
free_cpumask_var(data->freqdomain_cpus);
@@ -876,6 +917,7 @@ static struct freq_attr *acpi_cpufreq_attr[] = {
static struct cpufreq_driver acpi_cpufreq_driver = {
.verify = cpufreq_generic_frequency_table_verify,
.target_index = acpi_cpufreq_target,
+ .fast_switch = acpi_cpufreq_fast_switch,
.bios_limit = acpi_processor_get_bios_limit,
.init = acpi_cpufreq_cpu_init,
.exit = acpi_cpufreq_cpu_exit,