Add and use a special guard for cooling devices.

This allows quite a few error code paths to be simplified among
other things and brings in code size reduction for a good measure.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/5837621.DvuYhMxLoT@rjwysocki.net
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

In almost all places where a thermal zone's list of thermal instances
is walked, there is a check to match a specific trip point and it is
walked in vain whenever there are no cooling devices associated with
the given trip.

To address this, store the lists of thermal instances in trip point
descriptors instead of storing them in thermal zones and adjust all
code using those lists accordingly.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/5522726.Sb9uPGUboI@rjwysocki.net
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

Commit b6846826982b ("thermal: gov_step_wise: Restore passive polling
management") attempted to fix a Step-Wise thermal governor issue
introduced by commit 042a3d80f118 ("thermal: core: Move passive polling
management to the core"), which caused the governor to leave cooling
devices in high states, by partially reverting that commit.

However, this turns out to be insufficient on some systems due to
interactions between the governor code restored by commit b6846826982b
and the passive polling management in the thermal core.

For this reason, revert commit b6846826982b and make the governor set
the target cooling device state to the "lower" one as soon as the zone
temperature falls below the threshold of the trip point corresponding
to the given thermal instance, which means that thermal mitigation is
not necessary any more.

Before this change the "lower" cooling device state would be reached in
steps through the passive polling mechanism which was questionable for
three reasons: (1) cooling device were kept in high states when that was
not necessary (and it could adversely impact performance), (2) it only
worked for thermal zones with nonzero passive_delay_jiffies value, and
(3) passive polling belongs to the core and should not be hijacked by
governors for their internal purposes.

Fixes: b6846826982b ("thermal: gov_step_wise: Restore passive polling management")
Closes: https://lore.kernel.org/linux-pm/6759ce9f-281d-4fcd-bb4c-b784a1cc5f6e@oldschoolsolutions.biz
Reported-by: Jens Glathe <jens.glathe@oldschoolsolutions.biz>
Tested-by: Jens Glathe <jens.glathe@oldschoolsolutions.biz>
Link: https://patch.msgid.link/12464461.O9o76ZdvQC@rjwysocki.net
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Steev Klimaszewski <steev@kali.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>

Consider a thermal zone with one passive trip point, a cooling device
with 3 states (0, 1, 2) bound to it, passive polling enabled (nonzero
passive_delay_jiffies) and no regular polling (polling_delay_jiffies
equal to 0) that is managed by the Step-Wise governor.  Suppose that
the initial state of the cooling device is 0 and the zone temperature
is below the trip point to start with.

When the trip point is crossed, tz->passive is incremented by the
thermal core and the governor's .manage() callback is invoked.  It
sets 'throttle' to 'true' for the trip in question and
get_target_state() returns 1 for the instance corresponding to the
cooling device (say that 'upper' and 'lower' are set to 2 and 0 for
it, respectively), so its state changes to 1.

Passive polling is still active for the zone, so next time the
temperature is updated, the governor's .manage() callback will be
invoked again.  If the temperature is still rising, it will change
the state of the cooling device to 2.

Now suppose that next time the zone temperature is updated, it falls
below the trip point, so tz->passive is decremented for the zone (say
it becomes 0 then) and the governor's .manage() callbacks runs.

It finds that the temperature trend for the zone is 'falling' and
'throttle' will be set to 'false' for the trip in question, so the
cooling device's state will be changed to 1.  However, because
tz->polling is 0 for the zone, the governor's .manage() callback
may not be invoked again for a long time and the cooling device's
state will not be reset back to 0.

This can happen because commit 042a3d80f118 ("thermal: core: Move
passive polling management to the core") removed passive polling
management from the Step-Wise governor.

Before that change, thermal_zone_trip_update() would bump up
tz->passive when changing the target state for a thermal instance
from "no target" to a specific value and it would drop tz->passive
when changing it back to "no target" which would cause passive
polling to be active for the zone until the governor has reset the
states of all cooling devices.  In particular, in the example above
tz->passive would be incremented when changing the state of the
cooling device from 0 to 1 and then it would be still nonzero when
the state of the cooling device was changed from 2 to 1.

To prevent this problem from occurring, restore the passive polling
management in the Step-Wise governor by partially reverting the
commit in question and update the comment in the restored code
to explain its role more clearly.

Fixes: 042a3d80f118 ("thermal: core: Move passive polling management to the core")
Closes: https://lore.kernel.org/linux-pm/ZmVfcEOxmjUHZTSX@hovoldconsulting.com
Reported-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Passive polling is enabled by setting the 'passive' field in
struct thermal_zone_device to a positive value so long as the
'passive_delay_jiffies' field is greater than zero.  It causes
the thermal core to actively check the thermal zone temperature
periodically which in theory should be done after crossing a
passive trip point on the way up in order to allow governors to
react more rapidly to temperature changes and adjust mitigation
more precisely.

However, the 'passive' field in struct thermal_zone_device is currently
managed by governors which is quite problematic.  First of all, only
two governors, Step-Wise and Power Allocator, update that field at
all, so the other governors do not benefit from passive polling,
although in principle they should.  Moreover, if the zone governor is
changed from, say, Step-Wise to Fair-Share after 'passive' has been
incremented by the former, it is not going to be reset back to zero by
the latter even if the zone temperature falls down below all passive
trip points.

For this reason, make handle_thermal_trip() increment 'passive'
to enable passive polling for the given thermal zone whenever a
passive trip point is crossed on the way up and decrement it
whenever a passive trip point is crossed on the way down.  Also
remove the 'passive' field updates from governors and additionally
clear it in thermal_zone_device_init() to prevent passive polling
from being enabled after a system resume just beacuse it was enabled
before suspending the system.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>

Do some assorted cleanups in thermal_zone_trip_update():

 * Compute the trend value upfront.
 * Move old_target definition to the block where it is used.
 * Adjust white space around diagnostic messages and locking.
 * Use suitable field formatting in a message to avoid an explicit
   cast to int.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

In principle, the Step-Wise governor should take trip hysteresis into
account.  After all, once a trip has been crossed on the way up,
mitigation is still needed until it is crossed on the way down.

For this reason, make it use trip thresholds that are computed by
the core when trips are crossed, so as to apply mitigations in the
hysteresis rages of trips that were crossed on the way up, but have
not been crossed on the way down yet.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Make the Step-Wise governor use the new .manage() callback instead of
.throttle().

Even though using .throttle() is not particularly problematic for the
Step-Wise governor, using .manage() instead still allows it to reduce
overhead by updating all of the cooling devices once after setting
target values for all of the thermal instances.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Make it more clear from the code flow that the passive polling status
updates only take place for passive trip points.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

The step-wise governor's get_target_state() function contains redundant
braces, redundant parens and a redundant next_target local variable, so
get rid of all that stuff.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>