[PATCH v3 2/4] cpufreq: introduce cpufreq_driver_might_sleep
From: Michael Turquette <mturquette@baylibre.com>
Date: 2015-06-26 23:55:44
Also in:
lkml
Subsystem:
cpu frequency scaling framework, the rest · Maintainers:
"Rafael J. Wysocki", Viresh Kumar, Linus Torvalds
From: Michael Turquette <mturquette@baylibre.com> Some architectures and platforms perform CPU frequency transitions through a non-blocking method, while some might block or sleep. This distinction is important when trying to change frequency from interrupt context or in any other non-interruptable context, such as from the Linux scheduler. Describe this distinction with a cpufreq driver flag, CPUFREQ_DRIVER_WILL_NOT_SLEEP. The default is to not have this flag set, thus erring on the side of caution. cpufreq_driver_might_sleep() is also introduced in this patch. Setting the above flag will allow this function to return false. Cc: Rafael J. Wysocki <rafael@kernel.org> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Michael Turquette <mturquette@baylibre.com> --- drivers/cpufreq/cpufreq.c | 6 ++++++ include/linux/cpufreq.h | 9 +++++++++ 2 files changed, 15 insertions(+)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 28e59a4..e5296c0 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c@@ -112,6 +112,12 @@ bool have_governor_per_policy(void) } EXPORT_SYMBOL_GPL(have_governor_per_policy); +bool cpufreq_driver_might_sleep(void) +{ + return !(cpufreq_driver->flags & CPUFREQ_DRIVER_WILL_NOT_SLEEP); +} +EXPORT_SYMBOL_GPL(cpufreq_driver_might_sleep); + struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy) { if (have_governor_per_policy())
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 2ee4888..1f2c9a1 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h@@ -157,6 +157,7 @@ u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy); int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu); int cpufreq_update_policy(unsigned int cpu); bool have_governor_per_policy(void); +bool cpufreq_driver_might_sleep(void); struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy); #else static inline unsigned int cpufreq_get(unsigned int cpu)
@@ -314,6 +315,14 @@ struct cpufreq_driver { */ #define CPUFREQ_NEED_INITIAL_FREQ_CHECK (1 << 5) +/* + * Set by drivers that will never block or sleep during their frequency + * transition. Used to indicate when it is safe to call cpufreq_driver_target + * from non-interruptable context. Drivers must opt-in to this flag, as the + * safe default is that they might sleep. + */ +#define CPUFREQ_DRIVER_WILL_NOT_SLEEP (1 << 6) + int cpufreq_register_driver(struct cpufreq_driver *driver_data); int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);
--
1.9.1