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

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Message-ID: <2d8bcc54-e1f9-3d7b-e31a-8463c28dfecd@linaro.org>
Date:   Thu, 26 Mar 2020 20:47:30 +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 20:37, Rafael J. Wysocki wrote:
> On Thu, Mar 26, 2020 at 8:20 PM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>> 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'.
>
> So I wouldn't add the "get" thing at all if it has no users.

Ok

> Also it would be better to send this patch along with the other
> one depending on it.

Sure will resend along with the other patches.



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