linux-kernel - Re: [PATCH] powercap/drivers/idle_inject: Specify idle state max latency

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Date:   Thu, 26 Mar 2020 20:20:29 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "open list:POWER MANAGEMENT CORE" <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powercap/drivers/idle_inject: Specify idle state max
 latency

On 26/03/2020 20:14, Rafael J. Wysocki wrote:
> On Thu, Mar 26, 2020 at 3:48 PM Daniel Lezcano
> <daniel.lezcano@...aro.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@...aro.org> ---
>> drivers/powercap/idle_inject.c | 27 ++++++++++++++++++++++++++-
>> include/linux/idle_inject.h    |  6 ++++++ 2 files changed, 32
>> insertions(+), 1 deletion(-)

[ ... ]

>> + +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.

Do you mean a user for the set/get or the get only? If the latter,
there is no user yet I just added it to have an usual get/set helpers,
if that hurts, I can resend by removing it. If the former, there is a
patch I'm about to send which depends on the 'set'.


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