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doc: pm: Clarify a device pm note

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Clarify conditions that prevent the cpu to enter low power
state.

Fixes #69647

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
This commit is contained in:
Flavio Ceolin 2024-03-27 16:04:39 -07:00 • committed by Carles Cufí
commit 68c0c55419
1 changed files with 8 additions and 3 deletions
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11
doc/services/pm/device.rst
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@ -105,9 +105,14 @@ It is important to emphasize that this method has drawbacks (see above) and
.. note::
When using this method of device power management, the CPU will enter
a low power state only if no devices are in the middle of a hardware
transaction that cannot be interrupted.
When using this method of device power management, the CPU will not
enter a low-power state if a device cannot be suspended. For example,
if a device returns an error such as ``-EBUSY`` in response to the
``PM_DEVICE_ACTION_SUSPEND`` action, indicating it is in the middle of
a transaction that cannot be interrupted. Another condition that
prevents the CPU from entering a low-power state is if the option
:kconfig:option:`CONFIG_PM_NEED_ALL_DEVICES_IDLE` is set and a device
is marked as busy.
.. note::