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Diffstat (limited to 'Documentation/driver-api/pm/devices.rst')
| -rw-r--r-- | Documentation/driver-api/pm/devices.rst | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/driver-api/pm/devices.rst b/Documentation/driver-api/pm/devices.rst index 4a18ef9997c0..8add5b302a89 100644 --- a/Documentation/driver-api/pm/devices.rst +++ b/Documentation/driver-api/pm/devices.rst @@ -354,6 +354,20 @@ the phases are: ``prepare``, ``suspend``, ``suspend_late``, ``suspend_noirq``. is because all such devices are initially set to runtime-suspended with runtime PM disabled. + This feature also can be controlled by device drivers by using the + ``DPM_FLAG_NEVER_SKIP`` and ``DPM_FLAG_SMART_PREPARE`` driver power + management flags. [Typically, they are set at the time the driver is + probed against the device in question by passing them to the + :c:func:`dev_pm_set_driver_flags` helper function.] If the first of + these flags is set, the PM core will not apply the direct-complete + procedure described above to the given device and, consequenty, to any + of its ancestors. The second flag, when set, informs the middle layer + code (bus types, device types, PM domains, classes) that it should take + the return value of the ``->prepare`` callback provided by the driver + into account and it may only return a positive value from its own + ``->prepare`` callback if the driver's one also has returned a positive + value. + 2. The ``->suspend`` methods should quiesce the device to stop it from performing I/O. They also may save the device registers and put it into the appropriate low-power state, depending on the bus type the device is |