Re: [PATCH v5] drivers: thermal: clear all mitigation when thermal zone is disabled

[Manaf Meethalavalappu Pallikunhi]

On 1/31/2022 12:55 PM, Lukasz Luba wrote:
> Hi Manaf,
>
> On 1/27/22 6:11 PM, Manaf Meethalavalappu Pallikunhi 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 forever.
> >
> > To avoid above mentioned issue, add support to bind/unbind
> > governor from thermal zone during thermal zone mode change request
> > and clear all existing throttling in governor unbind_from_tz()
> > callback.
>
> I have one use case:
> This would be a bit dangerous, e.g. to switch governors while there is a
> high temperature. Although, sounds reasonable to left a 'default' state
> for a next governor.
I believe only way to change the governror via userspace at runtime.

Just re-evaluate thermal zone  (thermal_zone_device_update) immediately  
after

thermal_zone_device_set_policy()  in same policy_store() context, isn't 
it good enough ?

Not sure how a "default" state  can be reverted once governor change is 
done.

Re-evaluating thermal zone doesn't guarantee that it will recover previous

set default state for all governors, right ?

> > Suggested-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > Signed-off-by: Manaf Meethalavalappu Pallikunhi 
> > <quic_manafm@xxxxxxxxxxx>
> > ---
> >   drivers/thermal/gov_power_allocator.c |  3 +++
> >   drivers/thermal/gov_step_wise.c       | 26 ++++++++++++++++++++++++++
> >   drivers/thermal/thermal_core.c        | 31 
> > +++++++++++++++++++++++++++----
> >   3 files changed, 56 insertions(+), 4 deletions(-)
>
> Why only two governors need that change and not all?
> Because they don't have 'bind/unbind' callbacks, then maybe we should
> change that as well to make it consistent?
I will update other governors as well in v6
> Regards,
> Lukasz