linux-kernel - Re: [RFT][PATCH v2 1/2] PM / domains: Rework governor code to be more consistent

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Message-ID: <CAJZ5v0jXz7FCgmivjwLL-yfK2hHbW2bGAQGjb4YS4cY0JxDQ8w@mail.gmail.com>
Date:   Sat, 4 Nov 2017 12:24:15 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     ramesh.thomas@...el.com
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Tero Kristo <t-kristo@...com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Alex Shi <alex.shi@...aro.org>
Subject: Re: [RFT][PATCH v2 1/2] PM / domains: Rework governor code to be more consistent

On Sat, Nov 4, 2017 at 3:34 AM, Ramesh Thomas <ramesh.thomas@...el.com> wrote:
> On 2017-11-03 at 12:47:20 +0100, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> The genpd governor currently uses negative PM QoS values to indicate
>> the "no suspend" condition and 0 as "no restriction", but it doesn't
>> use them consistently.  Moreover, it tries to refresh QoS values for
>> already suspended devices in a quite questionable way.
>>
>> For the above reasons, rework it to be a bit more consistent.
>>
>> First off, note that dev_pm_qos_read_value() in
>> dev_update_qos_constraint() and __default_power_down_ok() is
>> evaluated for devices in suspend.  Moreover, that only happens if the
>> effective_constraint_ns value for them is negative (meaning "no
>> suspend").  It is not evaluated in any other cases, so effectively
>> the QoS values are only updated for devices in suspend that should
>> not have been suspended in the first place.  In all of the other
>> cases, the QoS values taken into account are the effective ones from
>> the time before the device has been suspended, so generally devices
>> need to be resumed and suspended again for new QoS values to take
>> effect anyway.  Thus evaluating dev_update_qos_constraint() in
>> those two places doesn't make sense at all, so drop it.
>>
>> Second, initialize effective_constraint_ns to 0 ("no constraint")
>> rather than to (-1) ("no suspend"), which makes more sense in
>> general and in case effective_constraint_ns is never updated
>> (the device is in suspend all the time or it is never suspended)
>> it doesn't affect the device's parent and so on.
>>
>> Finally, rework default_suspend_ok() to explicitly handle the
>> "no restriction" special case.
>>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> ---

[cut]

> Looks good to me.
>
> Acked-by: Ramesh Thomas <ramesh.thomas@...el.com>

Thanks!

Do you actually mean Reviewed-by?