powercap/drivers/idle_inject: Specify idle state max latency

Currently the idle injection framework uses the play_idle() function
which puts the current CPU in an idle state. The idle state is the
deepest one, as specified by the latency constraint when calling the
subsequent play_idle_precise() function with the INT_MAX.

The idle_injection is used by the cpuidle_cooling device which
computes the idle / run duration to mitigate the temperature by
injecting idle cycles. The cooling device has no control on the depth
of the idle state.

Allow finer control of the idle injection mechanism by allowing to
specify the latency for the idle state. Thus the cooling device has
the ability to have a guarantee on the exit latency of the idle states
it is injecting.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/20200429103644.5492-1-daniel.lezcano@linaro.org

diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c
index e9bbd3c42eefffab9792b72674cb7a57b8dc760e..c90f0990968bebf69d7b00e6c5484302982f0e62 100644 (file)
--- a/drivers/powercap/idle_inject.c
+++ b/drivers/powercap/idle_inject.c
@@ -61,12 +61,14 @@ struct idle_inject_thread {
  * @timer: idle injection period timer
  * @idle_duration_us: duration of CPU idle time to inject
  * @run_duration_us: duration of CPU run time to allow
+ * @latency_us: max allowed latency
  * @cpumask: mask of CPUs affected by idle injection
  */
 struct idle_inject_device {
        struct hrtimer timer;
        unsigned int idle_duration_us;
        unsigned int run_duration_us;
+       unsigned int latency_us;
        unsigned long cpumask[];
 };
 
@@ -138,7 +140,8 @@ static void idle_inject_fn(unsigned int cpu)
         */
        iit->should_run = 0;
 
-       play_idle(READ_ONCE(ii_dev->idle_duration_us));
+       play_idle_precise(READ_ONCE(ii_dev->idle_duration_us) * NSEC_PER_USEC,
+                         READ_ONCE(ii_dev->latency_us) * NSEC_PER_USEC);
 }
 
 /**
@@ -169,6 +172,16 @@ void idle_inject_get_duration(struct idle_inject_device *ii_dev,
        *idle_duration_us = READ_ONCE(ii_dev->idle_duration_us);
 }
 
+/**
+ * idle_inject_set_latency - set the maximum latency allowed
+ * @latency_us: set the latency requirement for the idle state
+ */
+void idle_inject_set_latency(struct idle_inject_device *ii_dev,
+                            unsigned int latency_us)
+{
+       WRITE_ONCE(ii_dev->latency_us, latency_us);
+}
+
 /**
  * idle_inject_start - start idle injections
  * @ii_dev: idle injection control device structure
@@ -297,6 +310,7 @@ struct idle_inject_device *idle_inject_register(struct cpumask *cpumask)
        cpumask_copy(to_cpumask(ii_dev->cpumask), cpumask);
        hrtimer_init(&ii_dev->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        ii_dev->timer.function = idle_inject_timer_fn;
+       ii_dev->latency_us = UINT_MAX;
 
        for_each_cpu(cpu, to_cpumask(ii_dev->cpumask)) {
 

diff --git a/include/linux/idle_inject.h b/include/linux/idle_inject.h
index a445cd1a36c5d8f08135f3b83376fd5762914555..91a8612b8bf9e2ea249fa96a1fc4f6f7fa31065e 100644 (file)
--- a/include/linux/idle_inject.h
+++ b/include/linux/idle_inject.h
@@ -26,4 +26,8 @@ void idle_inject_set_duration(struct idle_inject_device *ii_dev,
 void idle_inject_get_duration(struct idle_inject_device *ii_dev,
                                 unsigned int *run_duration_us,
                                 unsigned int *idle_duration_us);
+
+void idle_inject_set_latency(struct idle_inject_device *ii_dev,
+                            unsigned int latency_ns);
+
 #endif /* __IDLE_INJECT_H__ */