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When searching for the trip points that need to be set, the nearest
higher trip point's temperature is used for the high trip, while the
nearest lower trip point's temperature minus the hysteresis is used for
the low trip. The issue with this logic is that when the current
temperature is inside a trip point's hysteresis range, both high and low
trips will come from the same trip point. As a consequence instability
can still occur like this:
* the temperature rises slightly and enters the hysteresis range of a
trip point
* polling happens and updates the trip points to the hysteresis range
* the temperature falls slightly, exiting the hysteresis range, crossing
the trip point and triggering an IRQ, the trip points are updated
* repeat
So even though the current hysteresis implementation prevents
instability from happening due to IRQs triggering on the same
temperature value, both ways, it doesn't prevent it from happening due
to an IRQ on one way and polling on the other.
To properly implement a hysteresis behavior, when inside the hysteresis
range, don't update the trip points. This way, the previously set trip
points will stay in effect, which will in a way remember the previous
state (if the temperature signal came from above or below the range) and
therefore have the right trip point already set.
The exception is if there was no previous trip point set, in which case
a previous state doesn't exist, and so it's sensible to allow the
hysteresis range as trip points.
The following logs show the current behavior when running on a real
machine:
[ 202.524658] thermal thermal_zone0: new temperature boundaries: -2147483647 < x < 40000
203.562817: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=36986 temp=37979
[ 203.562845] thermal thermal_zone0: new temperature boundaries: 37000 < x < 40000
204.176059: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=37979 temp=40028
[ 204.176089] thermal thermal_zone0: new temperature boundaries: 37000 < x < 100000
205.226813: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=40028 temp=38652
[ 205.226842] thermal thermal_zone0: new temperature boundaries: 37000 < x < 40000
And with this patch applied:
[ 184.933415] thermal thermal_zone0: new temperature boundaries: -2147483647 < x < 40000
185.981182: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=36986 temp=37872
186.744685: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=37872 temp=40058
[ 186.744716] thermal thermal_zone0: new temperature boundaries: 37000 < x < 100000
187.773284: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=40058 temp=38698
Fixes: 060c034a9741 ("thermal: Add support for hardware-tracked trip points")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Co-developed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Define a new macro for_each_trip() to be used by the thermal core code
and thermal governors for walking trips in a given thermal zone.
Modify for_each_thermal_trip() to use this macro instead of an open-
coded loop over trips.
No intentional functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
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A trip index can be computed right away as a difference between the
value of a trip pointer pointing to the given trip object and the
start of the trips[] table in the given thermal zone, so change
thermal_zone_trip_id() accordingly.
No intentional functional impact (except for some speedup).
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
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The lockdep assertion in thermal_zone_trip_id() triggers when the
trip point sysfs attribute of a thermal instance is read, because
there is no thermal zone locking in that code path.
This is not verly useful, though, because there is no mechanism by which
the location of the trips[] table in a thermal zone or its size can
change after binding cooling devices to the trips in that thermal
zone and before those cooling devices are unbound from them. Thus
it is not in fact necessary to hold the thermal zone lock when
thermal_zone_trip_id() is called from trip_point_show() and so the
lockdep asserion in the former is invalid.
Accordingly, drop that lockdep assertion.
Fixes: 2c7b4bfadef0 ("thermal: core: Store trip pointer in struct thermal_instance")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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The lockdep assertion in for_each_thermal_trip() was added to possibly
catch incorrect usage of that function without the thermal zone lock.
However, it turns out that the ACPI thermal driver has a legitimate
reason to call for_each_thermal_trip() without locking.
Namely, it is called by acpi_thermal_bind_unbind_cdev() in the thermal
zone registration and unregistration paths. That function cannot acquire
the thermal zone lock by itself, because it calls functions that acquire
it, thermal_bind_cdev_to_trip() or thermal_unbind_cdev_from_trip().
However, it is invoked when the ACPI notify handler for the thermal
zone in question has not been registered yet (in the registration path)
or after that handler has been unregistered (in the unregistration
path). Therefore, when for_each_thermal_trip() is called by
acpi_thermal_bind_unbind_cdev(), thermal trip changes induced by the
platform firmware cannot take place and so the thermal zone's trips[]
table is effectively immutable. Hence, it is valid to call
for_each_thermal_trip() from acpi_thermal_bind_unbind_cdev() without
locking and the lockdep assertion in the former is in fact incorrect, so
remove it.
Fixes: d5ea889246b1 ("ACPI: thermal: Do not use trip indices for cooling device binding")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Add a wrapper around for_each_thermal_trip(), called
thermal_zone_for_each_trip(), that will invoke the former under the
thermal zone lock and pass its return value to the caller.
Two drivers will be modified subsequently to use this new function.
No functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
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Replace the integer trip number stored in struct thermal_instance with
a pointer to the relevant trip and adjust the code using the structure
in question accordingly.
The main reason for making this change is to allow the trip point to
cooling device binding code more straightforward, as illustrated by
subsequent modifications of the ACPI thermal driver, but it also helps
to clarify the overall design and allows the governor code overhead to
be reduced (through subsequent modifications).
The only case in which it adds complexity is trip_point_show() that
needs to walk the trips[] table to find the index of the given trip
point, but this is not a critical path and the interface that
trip_point_show() belongs to is problematic anyway (for instance, it
doesn't cover the case when the same cooling devices is associated
with multiple trip points).
This is a preliminary change and the affected code will be refined by
a series of subsequent modifications of thermal governors, the core and
the ACPI thermal driver.
The general functionality is not expected to be affected by this change.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
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It is invalid to call for_each_thermal_trip() on an unregistered thermal
zone anyway, and as per thermal_zone_device_register_with_trips(), the
trips[] table must be present if num_trips is greater than zero for the
given thermal zone.
Hence, the trips check in for_each_thermal_trip() is redundant and so it
can be dropped.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
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After recent changes in the ACPI thermal driver and in the Intel DTS
IOSF thermal driver, all thermal zone drivers are expected to use trip
tables for initialization and none of them should implement
.get_trip_type(), .get_trip_temp() or .get_trip_hyst() callbacks, so
drop these callbacks entirely from the core.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Rework the currently unused __for_each_thermal_trip() to pass original
pointers to struct thermal_trip objects to the callback, so it can be
used for updating trip data (e.g. temperatures), rename it to
for_each_thermal_trip() and make it available to modular drivers.
Suggested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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The thermal_core.c files contains a lot of functions handling
different thermal components like the governors, the trip points, the
cooling device, the OF cooling device, etc ...
This organization does not help to migrate to a more sane code where
there is a better self-encapsulation as all the components' internals
can be directly accessed from a single file.
For the sake of clarity, let's move the thermal trip points code in a
dedicated thermal_trip.c file and add a function to browse all the
trip points like we do with the thermal zones, the govenors and the
cooling devices.
The same can be done for the cooling devices and the governor code but
that will come later as the current work in the thermal framework is
to fix the trip point handling and use a generic trip point structure.
No functional changes intended.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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