Messages in this thread | | | Subject | Re: [PATCH v3 4/4] thermal/core: Fix thermal trip cross point | From | Zhang Rui <> | Date | Mon, 18 Jul 2022 13:30:30 +0800 |
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On Fri, 2022-07-15 at 23:09 +0200, Daniel Lezcano wrote: > The routine doing trip point crossing the way up or down is actually > wrong. > > A trip point is composed with a trip temperature and a hysteresis. > > The trip temperature is used to detect when the trip point is crossed > the way up. > > The trip temperature minus the hysteresis is used to detect when the > trip point is crossed the way down. > > > -----------low--------high------------| > |<--------->| > | hyst | > | | > | -|--> crossed the way up > | > <---|-- crossed the way down > > For that, there is a two point comparison: the current temperature > and > the previous temperature. > > The actual code assumes if the current temperature is greater than > the > trip temperature and the previous temperature was lesser, then the > trip point is crossed the way up. That is true only if we crossed the > way down the low temperature boundary from the previous temperature > or > if the hysteresis is zero. The temperature can decrease between the > low and high, so the trip point is not crossed the way down and then > increase again and cross the high temperature raising a new trip > point > crossed detection which is incorrect. The same scenario happens when > crossing the way down. > > The trip point crossing the way up and down must act as parenthesis, > a > trip point down must close a trip point up. Today we have multiple > trip point up without the corresponding trip point down. > > In order to fix that, we store the previous trip point which gives > the > information about the previous trip and we change the trip point > browsing order depending on the temperature trend: in the ascending > order when the temperature trend is raising, otherwise in the > descending order. > > As a sidenote, the thermal_zone_device structure has already the > prev_trip_low and prev_trip_high information which are used by the > thermal_zone_set_trips() function. This one can be changed to be > triggered by the trip temperature crossing function, which makes more > sense, and the two fields will disappear. > > Tested on a rk3399-rock960 with thermal stress and 4 trip points. > Also > tested with temperature emulation to create a temperature jump > directly to the second trip point. > > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> > --- > V3: > > - Use the ordered indexes introduced in the previous patch as the > trip could be not ordered > > V2: > - As spotted by Zhang Rui, the trip cross notification does not > work if the temperature drops and crosses two trip points in the > same update interval. In order to fix that, we browse the trip > point > in the ascending order when the temperature trend is raising, > otherwise in the descending order. > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>
> --- > drivers/thermal/thermal_core.c | 54 ++++++++++++++++++++++++-------- > -- > include/linux/thermal.h | 2 ++ > 2 files changed, 41 insertions(+), 15 deletions(-) > > diff --git a/drivers/thermal/thermal_core.c > b/drivers/thermal/thermal_core.c > index f02f38b66445..a5c5f6f4e42b 100644 > --- a/drivers/thermal/thermal_core.c > +++ b/drivers/thermal/thermal_core.c > @@ -354,30 +354,48 @@ static void handle_critical_trips(struct > thermal_zone_device *tz, > tz->ops->critical(tz); > } > > -static void handle_thermal_trip_crossed(struct thermal_zone_device > *tz, int trip, > +static void handle_thermal_trip_crossed(struct thermal_zone_device > *tz, int index, > int trip_temp, int trip_hyst, > enum thermal_trip_type > trip_type) > { > + int trip_low_temp = trip_temp - trip_hyst; > + int trip = tz->trips_indexes[index]; > + > if (tz->last_temperature == THERMAL_TEMP_INVALID) > return; > > - if (tz->last_temperature < trip_temp && > - tz->temperature >= trip_temp) { > - thermal_notify_tz_trip_up(tz->id, trip, > - tz->temperature); > - } > - > - if (tz->last_temperature >= trip_temp && > - tz->temperature < (trip_temp - trip_hyst)) { > - thermal_notify_tz_trip_down(tz->id, trip, > - tz->temperature); > + /* > + * Due to the hysteresis, a third information is needed to > + * detect when the temperature is wavering between the > + * trip_low_temp and the trip_temp. A trip point is crossed > + * the way up only if the temperature is above it while the > + * previous temperature was below *and* we crossed the > + * trip_temp_low before. The previous trip point give us the > + * previous trip point transition. The similar problem exists > + * when crossing the way down. > + * > + * Note the mechanism works only if the caller of the > function > + * invoke the function with the trip point ascending or > + * descending regarding the temperature trend. A temperature > + * drop trend will browse the trip point in the descending > + * order > + */ > + if (tz->last_temperature < trip_temp && tz->temperature >= > trip_temp && > + index != tz->prev_index) { > + thermal_notify_tz_trip_up(tz->id, trip, tz- > >temperature); > + tz->prev_index = index; > + } else if (tz->last_temperature >= trip_low_temp && tz- > >temperature < trip_low_temp && > + index == tz->prev_index) { > + thermal_notify_tz_trip_down(tz->id, trip, tz- > >temperature); > + tz->prev_index--; > } > } > > -static void handle_thermal_trip(struct thermal_zone_device *tz, int > trip) > +static void handle_thermal_trip(struct thermal_zone_device *tz, int > index) > { > enum thermal_trip_type type; > int trip_temp, hyst = 0; > + int trip = tz->trips_indexes[index]; > > /* Ignore disabled trip points */ > if (test_bit(trip, &tz->trips_disabled)) > @@ -388,7 +406,7 @@ static void handle_thermal_trip(struct > thermal_zone_device *tz, int trip) > if (tz->ops->get_trip_hyst) > tz->ops->get_trip_hyst(tz, trip, &hyst); > > - handle_thermal_trip_crossed(tz, trip, trip_temp, hyst, type); > + handle_thermal_trip_crossed(tz, index, trip_temp, hyst, > type); > > if (type == THERMAL_TRIP_CRITICAL || type == > THERMAL_TRIP_HOT) > handle_critical_trips(tz, trip, trip_temp, type); > @@ -428,6 +446,7 @@ static void thermal_zone_device_init(struct > thermal_zone_device *tz) > { > struct thermal_instance *pos; > tz->temperature = THERMAL_TEMP_INVALID; > + tz->prev_index = -1; > tz->prev_low_trip = -INT_MAX; > tz->prev_high_trip = INT_MAX; > list_for_each_entry(pos, &tz->thermal_instances, tz_node) > @@ -512,8 +531,13 @@ void thermal_zone_device_update(struct > thermal_zone_device *tz, > > tz->notify_event = event; > > - for (count = 0; count < tz->trips; count++) > - handle_thermal_trip(tz, count); > + if (tz->last_temperature <= tz->temperature) { > + for (count = 0; count < tz->trips; count++) > + handle_thermal_trip(tz, count); > + } else { > + for (count = tz->trips; count >= 0; count--) > + handle_thermal_trip(tz, count); > + } > } > EXPORT_SYMBOL_GPL(thermal_zone_device_update); > > diff --git a/include/linux/thermal.h b/include/linux/thermal.h > index 4c3b72536772..d512f21561f1 100644 > --- a/include/linux/thermal.h > +++ b/include/linux/thermal.h > @@ -125,6 +125,7 @@ struct thermal_cooling_device { > * @last_temperature: previous temperature read > * @emul_temperature: emulated temperature when using > CONFIG_THERMAL_EMULATION > * @passive: 1 if you've crossed a passive trip point, 0 > otherwise. > + * @prev_index: previous index pointing to the trip > point the thermal zone was > * @prev_low_trip: the low current temperature if you've crossed > a passive > trip point. > * @prev_high_trip: the above current temperature if you've > crossed a > @@ -161,6 +162,7 @@ struct thermal_zone_device { > int last_temperature; > int emul_temperature; > int passive; > + int prev_index; > int prev_low_trip; > int prev_high_trip; > atomic_t need_update;
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