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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Fri, 13 Oct 2023 12:07:09 +0200
Message-ID: <CAJZ5v0gHYAXDPxOVSuFTz0YSm5NRGsP0HqvvFsvqUXZ3OUMjDw@mail.gmail.com>
Subject: Re: [PATCH v1 0/6] thermal: core: Pass trip pointers to governor
 .throttle() callbacks
To:     Lukasz Luba <lukasz.luba@arm.com>
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Zhang Rui <rui.zhang@intel.com>
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Hi Lukasz,

On Fri, Oct 13, 2023 at 10:12 AM Lukasz Luba <lukasz.luba@arm.com> wrote:
>
> Hi Rafael,
>
>
> On 10/6/23 18:38, Rafael J. Wysocki wrote:
> > Hi All,
> >
> > While working on https://lore.kernel.org/linux-pm/4846448.GXAFRqVoOG@kreacher/
> > I started to change thermal governors so as to reduce the usage of trip
> > indices in them.  At that time, I was concerned that they could not be
> > replaced with trip pointers overall, because they were needed in certain
> > situations (tracing, debug messages, userspace governor) and computing them
> > whenever they were needed would be extra overhead with relatively weak
> > justification.  In the meantime, however, I realized that for a given trip
> > pointer, it is actually trivial to compute the corresponding index: it is
> > sufficient to subtract the start of the trips[] table in the thermal zone
> > containing the trip from that trip pointer for this purpose.  Patch [1/6]
> > modifies thermal_zone_trip_id() in accordance with this observation.
> >
> > Now that the cost of computing a trip index for a given trip pointer and
> > thermal zone is not a concern any more, the governors can be generally
> > switched over to using trip pointers for representing trips.  One of the
> > things they need to do sometimes, though, is to iterate over trips in a
> > given thermal zone (the core needs to do that too, of course) and
> > for_each_thermal_trip() is somewhat inconvenient for this purpose, because
> > it requires callback functions to be defined and in some cases new data
> > types need to be introduced just in order to use it.  For this reason,
> > patch [2/6] adds a macro for iterating over trip points in a given thermal
> > zone with the help of a trip pointer and changes for_each_thermal_trip() to
> > use that macro internally.
> >
> > Patches [3-5/6] change individual governors to prepare them for using trip
> > pointers everywhere for representing trips, except for the trip argument of
> > the .throttle() callback and patch [6/6] finally changes the .throttle()
> > callback definition so that it takes a trip pointer as the argument
> > representing the trip.
> >
> > Please refer to the individual patch changelogs for details.
> >
> > Thanks!
> >
> >
> >
>
> I have issues to apply this series, could you tell me the best
> base branch from your tree?
>
> I will give it a try on my boards and review.

It is there in the thermal-core branch of linux-pm.git.

Thanks!