mmc: enable MMC/SD/SDIO device to suspend/resume asynchronously

Now, PM core supports asynchronous suspend/resume mode for devices
during system suspend/resume, and the power state transition of one
device may be completed in separate kernel thread. PM core ensures
all power state transition dependency between devices. This patch
enables MMC/SD/SDIO card and SDIO function devices to suspend/resume
asynchronously. This will take advantage of multicore and improve
system suspend/resume speed. After applying this patch and enabling
all SDIO function's child devices to suspend/resume asynchronously
on ASUS T100TA, the system suspend-to-idle time is reduced from
1645ms to 1108ms, and the system resume time is reduced from 940ms
to 918ms.
Signed-off-by: Zhonghui Fu <zhonghui.fu@linux.intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/bus.c

@@ -349,6 +349,8 @@ int mmc_add_card(struct mmc_card *card)
 
 	card->dev.of_node = mmc_of_find_child_device(card->host, 0);
 
+	device_enable_async_suspend(&card->dev);
+
 	ret = device_add(&card->dev);
 	if (ret)
 		return ret;

drivers/mmc/core/sdio_bus.c

@@ -322,6 +322,7 @@ int sdio_add_func(struct sdio_func *func)
 
 	sdio_set_of_node(func);
 	sdio_acpi_set_handle(func);
+	device_enable_async_suspend(&func->dev);
 	ret = device_add(&func->dev);
 	if (ret == 0)
 		sdio_func_set_present(func);