Subject: [PATCH RFC 16/27] ARM: cpuidle: Record the next wakeup event of the CPU

From: [email-masked] (Kevin Hilman)
Date: Thu, 19 Nov 2015 15:35:47 -0800

Lina Iyer <[email-masked]> writes:

> Reading the next wakeup of the CPU can only be realiably done only from
> that CPU. In the idle enter path record the next wake up of the CPU. The
> information is useful to determine the sleep time left for the CPU.
>
> Signed-off-by: Lina Iyer <[email-masked]>
> ---
>  drivers/cpuidle/cpuidle-arm.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
> index 8e72a23..b3133ef 100644
> --- a/drivers/cpuidle/cpuidle-arm.c
> +++ b/drivers/cpuidle/cpuidle-arm.c
> @@ -18,9 +18,11 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/pm_domain.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/slab.h>
>  #include <linux/rcupdate.h>
> +#include <linux/tick.h>
>  
>  #include <asm/cpuidle.h>
>  
> @@ -49,7 +51,9 @@ static int arm_enter_idle_state(struct cpuidle_device *dev,
>  	ret = cpu_pm_enter();
>  	if (!ret) {
>  		struct device *cpu_dev = get_cpu_device(dev->cpu);
> +		struct generic_pm_domain_data *gpd = dev_gpd_data(cpu_dev);
>  
> +		gpd->td.next_wakeup = tick_nohz_get_next_wakeup();
>  		RCU_NONIDLE(pm_runtime_put_sync_suspend(cpu_dev));

Maybe set this back to zero atomicaly, after wakeup?

Checking for non-zero that might be another way for the domain goveror that there
haven't been any CPU wakeups since the CPUs have gone idle.

Kevin