linux-kernel - Re: [PATCH v2 2/5] thermal: trip: Make thermal_zone_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <CAJZ5v0hNX03dhSO5rWBhK8Fyzu1zH-aLhrTkm_b0zhMQr_W1Sw@mail.gmail.com>
Date: Tue, 11 Jun 2024 20:43:27 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Lukasz Luba <lukasz.luba@....com>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v2 2/5] thermal: trip: Make thermal_zone_set_trips() use
 trip thresholds

On Mon, Jun 10, 2024 at 8:01 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> On 28/05/2024 18:51, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Modify thermal_zone_set_trips() to use trip thresholds instead of
> > computing the low temperature for each trip to avoid deriving both
> > the high and low temperature levels from the same trip (which may
> > happen if the zone temperature falls into the hysteresis range of
> > one trip).
> >
> > Accordingly, make __thermal_zone_device_update() call
> > thermal_zone_set_trips() later, when threshold values have been
> > updated for all trips.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >
> > v1 -> v2: Rebase.
> >
> > ---
> >   drivers/thermal/thermal_core.c |    4 ++--
> >   drivers/thermal/thermal_trip.c |   14 ++++----------
> >   2 files changed, 6 insertions(+), 12 deletions(-)
> >
> > Index: linux-pm/drivers/thermal/thermal_core.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_core.c
> > +++ linux-pm/drivers/thermal/thermal_core.c
> > @@ -513,13 +513,13 @@ void __thermal_zone_device_update(struct
> >       if (tz->temperature == THERMAL_TEMP_INVALID)
> >               return;
> >
> > -     thermal_zone_set_trips(tz);
> > -
> >       tz->notify_event = event;
> >
> >       for_each_trip_desc(tz, td)
> >               handle_thermal_trip(tz, td, &way_up_list, &way_down_list);
>
> Would it make sense to use the for_each_trip_desc() loop here and update
> low and high on the fly in this loop ?
>
> If a trip point is crossed the way up or down, then
> handle_thermal_trip() returns a value which in turn results in updating
> low and high. If low and high are changed then the we call
> thermal_zone_set_trips() after the loop.
>
> The results for the thermal_zone_set_trips() will be the loop, the low,
> high, prev_low_trip and prev_high_trip variables going away.
>
> The resulting function should be:
>
> void thermal_zone_set_trips(struct thermal_zone_device *tz, int low, int
> high)
> {
>          int ret;
>
>          lockdep_assert_held(&tz->lock);
>
>          if (!tz->ops.set_trips)
>                  return;
>
>          /*
>
>
>           * Set a temperature window. When this window is left the
> driver
>
>           * must inform the thermal core via thermal_zone_device_update.
>
>
>           */
>          ret = tz->ops.set_trips(tz, low, high);
>          if (ret)
>                  dev_err(&tz->device, "Failed to set trips: %d\n", ret);
> }

So you essentially mean moving the for_each_trip_desc() loop from
thermal_zone_set_trips() to __thermal_zone_device_update() IIUC.

The caveat is that it is not necessary to run this loop at all if
tz->ops.set_trips is NULL.

I was thinking about folding the entire thermal_zone_set_trips() into
the caller, but that would be a different patch.

>
> But if you consider that is an additional change, then:

I do.

> Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>

Thank you!

>
> > +     thermal_zone_set_trips(tz);
> > +
> >       list_sort(&way_up_list, &way_up_list, thermal_trip_notify_cmp);
> >       list_for_each_entry(td, &way_up_list, notify_list_node)
> >               thermal_trip_crossed(tz, &td->trip, governor, true);
> > Index: linux-pm/drivers/thermal/thermal_trip.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_trip.c
> > +++ linux-pm/drivers/thermal/thermal_trip.c
> > @@ -88,17 +88,11 @@ void thermal_zone_set_trips(struct therm
> >               return;
> >
> >       for_each_trip_desc(tz, td) {
> > -             const struct thermal_trip *trip = &td->trip;
> > -             int trip_low;
> > +             if (td->threshold < tz->temperature && td->threshold > low)
> > +                     low = td->threshold;
> >
> > -             trip_low = trip->temperature - trip->hysteresis;
> > -
> > -             if (trip_low < tz->temperature && trip_low > low)
> > -                     low = trip_low;
> > -
> > -             if (trip->temperature > tz->temperature &&
> > -                 trip->temperature < high)
> > -                     high = trip->temperature;
> > +             if (td->threshold > tz->temperature && td->threshold < high)
> > +                     high = td->threshold;
> >       }
> >
> >       /* No need to change trip points */
> >
> >
> >
>
> --
> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
>
> Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
> <http://twitter.com/#!/linaroorg> Twitter |
> <http://www.linaro.org/linaro-blog/> Blog
>