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

[Lina Iyer <lina.iyer@linaro.org>]

On Thu, Nov 19 2015 at 16:35 -0700, Kevin Hilman wrote:
>Lina Iyer <lina.iyer@linaro.org> 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 <lina.iyer@linaro.org>
>> ---
>>  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.
>
I set it to 0 below.

The reference counting by the GET_PUT tells the domain if a device is
suspended. I see that as a redudant information. May be I am not getting
your point.

-- Lina
>Kevin