This function is called at initialization when power_allocator governor is set, and used to parametrize how the thermal manager shoud work. By reading its documentation, this function fix a switch_on trip point (i.e. first passive trip point seen during a scan of all trip points for that thermal_zone_device) and a max_desired_temperature trip point (i. e. last seen passive or active trip point during the scan). At last, if there is neither a passive nor an active trip point, the governor does nothing.
If a critical trip point is defined before a passive trip point, the governor will not work, even if there is a passive or active trip point declared after the critical point. For instance, on an Odroid-XU3/4 with a Samsung Exynos 5422 CPU, trip points are set as "active" first, "critical", then "passive". https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi?h=linux-4.18.y#n53 There is no documentation constraining to an order in the definition of trip points neither in the thermal manager nor in power_allocator. Thus, dts contributors could choose any order to define a thermal-zones, and set the "critical" trip point first, breaking this thermal governor. On Mon, 24 Sep 2018 at 17:45, Eduardo Valentin <edubez...@gmail.com> wrote: > > Hey, > > On Fri, Sep 21, 2018 at 02:06:09PM +0100, Willy Wolff wrote: > > If a trip of type critical is defined before any trip of passive > > or active type, power_allocator governor will not switch on. > > > But, if a critical trip is reached, the expectation is to perform a > thermal shutdown. Why would you expect to have power allocator > to be activated during the process of a shutdown? > > > > > Signed-off-by: Willy Wolff <willy.mh.wolff...@gmail.com> > > --- > > drivers/thermal/power_allocator.c | 2 -- > > 1 file changed, 2 deletions(-) > > > > diff --git a/drivers/thermal/power_allocator.c > > b/drivers/thermal/power_allocator.c > > index 3055f9a12a17..6544b68e3ebf 100644 > > --- a/drivers/thermal/power_allocator.c > > +++ b/drivers/thermal/power_allocator.c > > @@ -496,8 +496,6 @@ static void get_governor_trips(struct > > thermal_zone_device *tz, > > } > > } else if (type == THERMAL_TRIP_ACTIVE) { > > last_active = i; > > - } else { > > - break; > > } > > } > > > > -- > > 2.11.0 > >
