rtc: omap: add runtime pm support

OMAP1 RTC driver is used in multiple devices like, OMAPL138 and AM33XX.
Driver currently doesn't handle any clocks, which may be right for OMAP1
architecture but in case of AM33XX, the clock/module needs to be enabled
in order to access the registers.

So convert this driver to runtime pm, which internally handles rest.

[[e-mail]: handle error path]
Signed-off-by: Vaibhav Hiremath <[e-mail]>
Signed-off-by: Afzal Mohammed <[e-mail]>
Acked-by: Sekhar Nori <[e-mail]>
Cc: Grant Likely <[e-mail]>
Cc: Sekhar Nori <[e-mail]>
Cc: Kevin Hilman <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Alessandro Zummo <[e-mail]>
Cc: Daniel Mack <[e-mail]>
Cc: Vaibhav Hiremath <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-omap.c

···
 #include <linux/platform_device.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/pm_runtime.h>
 
 #include <asm/io.h>
 
···
 		goto fail;
 	}
 
+	/* Enable the clock/module so that we can access the registers */
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_get_sync(&pdev->dev);
+
 	id_entry = platform_get_device_id(pdev);
 	if (id_entry && (id_entry->driver_data & OMAP_RTC_HAS_KICKER)) {
 		rtc_writel(KICK0_VALUE, OMAP_RTC_KICK0_REG);
···
 fail0:
 	if (id_entry && (id_entry->driver_data & OMAP_RTC_HAS_KICKER))
 		rtc_writel(0, OMAP_RTC_KICK0_REG);
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
 	iounmap(rtc_base);
 fail:
 	release_mem_region(mem->start, resource_size(mem));
···
 	rtc_device_unregister(rtc);
 	if (id_entry && (id_entry->driver_data & OMAP_RTC_HAS_KICKER))
 		rtc_writel(0, OMAP_RTC_KICK0_REG);
+
+	/* Disable the clock/module */
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
 	iounmap(rtc_base);
 	release_mem_region(mem->start, resource_size(mem));
 	return 0;
···
 	else
 		rtc_write(0, OMAP_RTC_INTERRUPTS_REG);
 
+	/* Disable the clock/module */
+	pm_runtime_put_sync(&pdev->dev);
+
 	return 0;
 }
 
 static int omap_rtc_resume(struct platform_device *pdev)
 {
+	/* Enable the clock/module so that we can access the registers */
+	pm_runtime_get_sync(&pdev->dev);
+
 	if (device_may_wakeup(&pdev->dev))
 		disable_irq_wake(omap_rtc_alarm);
 	else