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SubjectRe: [PATCH] powercap/drivers/idle_inject: Specify idle state max latency
On Thu, Mar 26, 2020 at 3:48 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> 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.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
> drivers/powercap/idle_inject.c | 27 ++++++++++++++++++++++++++-
> include/linux/idle_inject.h | 6 ++++++
> 2 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c
> index cd1270614cc6..15e6f9b8023f 100644
> --- 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 int cpumask[0];
> };
>
> @@ -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 +172,27 @@ 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_get_latency - get the allowed latency
> + *
> + * Return: an unsigned int corresponding to the latency requirement
> + * for the idle state
> + */
> +unsigned int idle_inject_get_latency(struct idle_inject_device *ii_dev)
> +{
> + return READ_ONCE(ii_dev->latency_us);
> +}
> +
> /**
> * idle_inject_start - start idle injections
> * @ii_dev: idle injection control device structure
> @@ -297,6 +321,7 @@ 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 a445cd1a36c5..b573fee589b9 100644
> --- a/include/linux/idle_inject.h
> +++ b/include/linux/idle_inject.h
> @@ -26,4 +26,10 @@ 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);
> +
> +unsigned int idle_inject_get_latency(struct idle_inject_device *ii_dev);
> +
> #endif /* __IDLE_INJECT_H__ */
> --

I would like to see a user of idle_inject_get_latency() before this goes in.

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