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mmc: sdio: support suspend/resume while runtime suspended

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Bring SDIO devices back to full power before their suspend
handler is invoked.

Doing so ensures that SDIO suspend/resume semantics are
maintained (drivers still get to decide whether their
card should be removed or kept during system suspend,
and at what power state), and that SDIO suspend/resume
execution paths are unchanged.

This is achieved by resuming a runtime-suspended SDIO device
in its ->prepare() PM callback (similary to the PCI subsystem).

Since the PM core always increments the run-time usage
counter before calling the ->prepare() callback and decrements
it after calling the ->complete() callback, it is guaranteed
that when the system will come out of suspend, our device's
power state will reflect its runtime PM usage counter.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
This commit is contained in:
Ohad Ben-Cohen
2010-10-02 13:54:13 +02:00
committed by Chris Ball
parent 87973ba27b
commit ed2a978594
1 changed files with 29 additions and 0 deletions
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29
drivers/mmc/core/sdio_bus.c
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@ -189,12 +189,41 @@ out:
#ifdef CONFIG_PM_RUNTIME
static int sdio_bus_pm_prepare(struct device *dev)
{
/*
* Resume an SDIO device which was suspended at run time at this
* point, in order to allow standard SDIO suspend/resume paths
* to keep working as usual.
*
* Ultimately, the SDIO driver itself will decide (in its
* suspend handler, or lack thereof) whether the card should be
* removed or kept, and if kept, at what power state.
*
* At this point, PM core have increased our use count, so it's
* safe to directly resume the device. After system is resumed
* again, PM core will drop back its runtime PM use count, and if
* needed device will be suspended again.
*
* The end result is guaranteed to be a power state that is
* coherent with the device's runtime PM use count.
*
* The return value of pm_runtime_resume is deliberately unchecked
* since there is little point in failing system suspend if a
* device can't be resumed.
*/
pm_runtime_resume(dev);
return 0;
}
static const struct dev_pm_ops sdio_bus_pm_ops = {
SET_RUNTIME_PM_OPS(
pm_generic_runtime_suspend,
pm_generic_runtime_resume,
pm_generic_runtime_idle
)
.prepare = sdio_bus_pm_prepare,
};
#define SDIO_PM_OPS_PTR (&sdio_bus_pm_ops)