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    SubjectRe: [PATCH update x2] PM: Introduce core framework for run-time PM of I/O devices (rev. 13)
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    On Friday 07 August 2009, Alan Stern wrote:
    > On Thu, 6 Aug 2009, Rafael J. Wysocki wrote:
    >
    > > Hi,
    > >
    > > The patch below should address all of your most recent comments.
    >
    > Only two comments.
    >
    >
    > > +static int __pm_request_idle(struct device *dev)
    > > +{
    > ...
    > > + if (dev->power.request_pending) {
    > > + /* Any requests other then RPM_REQ_IDLE take precedence. */
    > > + if (dev->power.request != RPM_REQ_NONE)
    >
    > Replace != with ==.

    Good catch, thanks!

    > > + dev->power.request = RPM_REQ_IDLE;
    > > + else if (dev->power.request != RPM_REQ_IDLE)
    > > + retval = -EAGAIN;
    > > + return retval;
    >
    >
    > > --- linux-2.6.orig/drivers/base/dd.c
    > > +++ linux-2.6/drivers/base/dd.c
    > ...
    > > @@ -306,6 +317,8 @@ static void __device_release_driver(stru
    > >
    > > drv = dev->driver;
    > > if (drv) {
    > > + pm_runtime_disable(dev);
    > > +
    > > driver_sysfs_remove(dev);
    > >
    > > if (dev->bus)
    > > @@ -324,6 +337,8 @@ static void __device_release_driver(stru
    > > blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
    > > BUS_NOTIFY_UNBOUND_DRIVER,
    > > dev);
    > > +
    > > + pm_runtime_enable(dev);
    > > }
    > > }
    >
    > We may need to be more careful here. The driver's remove method may
    > want to do some runtime PM stuff to the device before giving up
    > control. On the other hand I'm not sure what _should_ be done here, so
    > I can't suggest anything better.

    Hmm. Perhaps we can do something along the lines of our .probe() handling.
    Namely, call

    pm_runtime_disable(dev);
    pm_runtime_get_noresume(dev);
    pm_runtime_enable(dev);

    before and

    pm_runtime_put_noidle()

    after? Then, if the driver's or bus type's .remove() needs to resume, it will
    be able to do that right away and if it wants to suspend, it can always call
    pm_runtime_put*(), because our pm_runtime_put_noidle() won't decrease the
    usage counter below zero.

    At the same time we can avoid "leftover" suspends that could interfere with
    .remove() in case it needs to access the hardware.

    Best,
    Rafael


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