mmc: sdio: support suspend/resume while runtime suspended
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>
diff --git a/drivers/mmc/core/sdio_bus.c b/drivers/mmc/core/sdio_bus.c
index 3637483..2716c7a 100644
--- a/drivers/mmc/core/sdio_bus.c
+++ b/drivers/mmc/core/sdio_bus.c
@@ -189,12 +189,41 @@
#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)