The DryIce-based RTC supports alarms that trigger an interrupt.

Add an option to configure this interrupt as a wakeup source that wakes the
system up from standby mode.

Signed-off-by: Martin Kaiser <redacted>
---
v2:
 - unconditionally declare rtc-imxdi as wakeup source
 - use dev_pm_set_wake_irq instead of manually coding suspend and resume

simple test (no need to configure the wakeup source via sysfs any more)

   [root@board ]# rtcwake -s 3 -m mem
   wakeup from "mem" at Fri Apr 30 09:23:52 2021
   ...
   [root@board ]#

 drivers/rtc/rtc-imxdi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/rtc/rtc-imxdi.c b/drivers/rtc/rtc-imxdi.c
index c1806f4d68e7..4b712e5ab08a 100644
--- a/drivers/rtc/rtc-imxdi.c
+++ b/drivers/rtc/rtc-imxdi.c

@@ -24,6 +24,7 @@
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
 #include <linux/rtc.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>

@@ -811,6 +812,9 @@ static int __init dryice_rtc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, imxdi);
 
+	device_init_wakeup(&pdev->dev, true);
+	dev_pm_set_wake_irq(&pdev->dev, norm_irq);
+