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    Subject[PATCH 1/2 v2] PM / Sleep: Simplify generic system suspend callbacks
    Date
    From: Rafael J. Wysocki <rjw@sisk.pl>
    Subject: PM / Sleep: Simplify generic system suspend callbacks

    The pm_runtime_suspended() check in __pm_generic_call() doesn't
    really help and may cause problems to happen, because in some cases
    the system suspend callbacks need to be called even if the given
    device has been suspended by runtime PM. For example, if the device
    generally supports remote wakeup and is not enabled to wake up
    the system from sleep, it should be prevented from generating wakeup
    signals during system suspend and that has to be done by the
    suspend callbacks that the pm_runtime_suspended() check prevents from
    being executed.

    Similarly, it may not be a good idea to unconditionally change
    the runtime PM status of the device to 'active' in
    __pm_generic_resume(), because the driver may want to leave the
    device in the 'suspended' state, depending on what happened to it
    before the system suspend and whether or not it is enabled to
    wake up the system.

    For the above reasons, remove the pm_runtime_suspended()
    check from __pm_generic_call() and remove the code changing the
    device's runtime PM status from __pm_generic_resume().

    Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
    ---
    drivers/base/power/generic_ops.c | 24 ++++++------------------
    1 file changed, 6 insertions(+), 18 deletions(-)

    Index: linux/drivers/base/power/generic_ops.c
    ===================================================================
    --- linux.orig/drivers/base/power/generic_ops.c
    +++ linux/drivers/base/power/generic_ops.c
    @@ -97,16 +97,16 @@ int pm_generic_prepare(struct device *de
    * @event: PM transition of the system under way.
    * @bool: Whether or not this is the "noirq" stage.
    *
    - * If the device has not been suspended at run time, execute the
    - * suspend/freeze/poweroff/thaw callback provided by its driver, if defined, and
    - * return its error code. Otherwise, return zero.
    + * Execute the suspend/freeze/poweroff/thaw callback provided by the driver of
    + * @dev, if defined, and return its error code. Return 0 if the callback is
    + * not present.
    */
    static int __pm_generic_call(struct device *dev, int event, bool noirq)
    {
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
    int (*callback)(struct device *);

    - if (!pm || pm_runtime_suspended(dev))
    + if (!pm)
    return 0;

    switch (event) {
    @@ -217,14 +217,12 @@ EXPORT_SYMBOL_GPL(pm_generic_thaw);
    * @bool: Whether or not this is the "noirq" stage.
    *
    * Execute the resume/resotre callback provided by the @dev's driver, if
    - * defined. If it returns 0, change the device's runtime PM status to 'active'.
    - * Return the callback's error code.
    + * defined, and return its error code. Return 0 if the callback is not present.
    */
    static int __pm_generic_resume(struct device *dev, int event, bool noirq)
    {
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
    int (*callback)(struct device *);
    - int ret;

    if (!pm)
    return 0;
    @@ -241,17 +239,7 @@ static int __pm_generic_resume(struct de
    break;
    }

    - if (!callback)
    - return 0;
    -
    - ret = callback(dev);
    - if (!ret && !noirq && pm_runtime_enabled(dev)) {
    - pm_runtime_disable(dev);
    - pm_runtime_set_active(dev);
    - pm_runtime_enable(dev);
    - }
    -
    - return ret;
    + return callback ? callback(dev) : 0;
    }

    /**


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