Re: [PATCH v2] thermal/core: Clear all mitigation when thermal zone is disabled

[Manaf Meethalavalappu Pallikunhi]

On 12/30/2021 9:39 PM, Rafael J. Wysocki wrote:
> On Wed, Dec 29, 2021 at 8:03 AM Manaf Meethalavalappu Pallikunhi
> <quic_manafm@xxxxxxxxxxx> wrote:
> > Whenever a thermal zone is in trip violated state, there is a chance
> > that the same thermal zone mode can be disabled either via thermal
> > core API or via thermal zone sysfs. Once it is disabled, the framework
> > bails out any re-evaluation of thermal zone. It leads to a case where
> > if it is already in mitigation state, it will stay the same state
> > until it is re-enabled.
> You seem to be arguing that disabling a thermal zone should prevent it
> from throttling anything, which is reasonable, but I'm not sure if the
> change below is sufficient for that.
>
> > To avoid above mentioned issue, on thermal zone disable request
> > reset thermal zone and clear mitigation for each trip explicitly.
> >
> > Signed-off-by: Manaf Meethalavalappu Pallikunhi <quic_manafm@xxxxxxxxxxx>
> > ---
> >   drivers/thermal/thermal_core.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> > index 51374f4..5f4e35b 100644
> > --- a/drivers/thermal/thermal_core.c
> > +++ b/drivers/thermal/thermal_core.c
> > @@ -427,6 +427,7 @@ static int thermal_zone_device_set_mode(struct thermal_zone_device *tz,
> >                                          enum thermal_device_mode mode)
> >   {
> >          int ret = 0;
> > +       int trip;
> This can be declared in the block in which it is used.
Sure, will update in next patch version
> >          mutex_lock(&tz->lock);
> >
> > @@ -449,8 +450,14 @@ static int thermal_zone_device_set_mode(struct thermal_zone_device *tz,
> >
> >          if (mode == THERMAL_DEVICE_ENABLED)
> The coding style asks for braces here if they are used after the else.
Sure will update in next version
> >                  thermal_notify_tz_enable(tz->id);
> > -       else
> > +       else {
> > +               /* make sure all previous throttlings are cleared */
> > +               thermal_zone_device_init(tz);
> > +               for (trip = 0; trip < tz->trips; trip++)
> > +                       handle_thermal_trip(tz, trip);
> So I'm not sure if this makes the throttling go away in all cases (eg.
> what if the current temperature is still above the given trip at this
> point?).

The thermal_zone_device_init() will reset current temperature with THERMAL_TEMP_INVALID. Then the following API
thandle_thermal_trip() doesn't call get_temp to sensor driver again instead it will use this reset temperature
value for each trip re-evaluation. Hence  for above mentioned case, I think it will clear the throttling
irrespective of what is the actual current temperature at that instant. Otherwise please correct me

May I know is there any other possible cases where throttling will not go away completely ?

> > +
> >                  thermal_notify_tz_disable(tz->id);
> > +       }
> >
> >          return ret;
> >   }