rtc: ds1307: Support optional wakeup interrupt source

With the recent pinctrl-single changes, SoCs such as Texas
Instrument's OMAP processors can treat wake-up events from deeper idle
states as interrupts.

Let's add support for the optional second interrupt for wake-up using
the generic wakeirq support added in commit 4990d4fe ("PM /
Wakeirq: Add automated device wake IRQ handling")

Finally, to pass the wake-up interrupt in the dts file,
interrupts-extended property needs to be passed.

This is similar in approach to commit 2a0b965c ("serial: omap: Add
support for optional wake-up") + ee83bd3b ("serial: omap: Switch
wake-up interrupt to generic wakeirq")
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-ds1307.c

@@ -15,6 +15,9 @@
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/pm_wakeirq.h>
 #include <linux/rtc/ds1307.h>
 #include <linux/rtc.h>
 #include <linux/slab.h>
@@ -114,6 +117,7 @@ struct ds1307 {
 #define HAS_ALARM	1		/* bit 1 == irq claimed */
 	struct i2c_client	*client;
 	struct rtc_device	*rtc;
+	int			wakeirq;
 	s32 (*read_block_data)(const struct i2c_client *client, u8 command,
 			       u8 length, u8 *values);
 	s32 (*write_block_data)(const struct i2c_client *client, u8 command,
@@ -1156,6 +1160,8 @@ static int ds1307_probe(struct i2c_client *client,
 	}
 
 	if (want_irq) {
+		struct device_node *node = client->dev.of_node;
+
 		err = devm_request_threaded_irq(&client->dev,
 						client->irq, NULL, irq_handler,
 						IRQF_SHARED | IRQF_ONESHOT,
@@ -1163,13 +1169,34 @@ static int ds1307_probe(struct i2c_client *client,
 		if (err) {
 			client->irq = 0;
 			dev_err(&client->dev, "unable to request IRQ!\n");
-		} else {
+			goto no_irq;
+		}
 
-			set_bit(HAS_ALARM, &ds1307->flags);
-			dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
+		set_bit(HAS_ALARM, &ds1307->flags);
+		dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
+
+		/* Currently supported by OF code only! */
+		if (!node)
+			goto no_irq;
+
+		err = of_irq_get(node, 1);
+		if (err <= 0) {
+			if (err == -EPROBE_DEFER)
+				goto exit;
+			goto no_irq;
+		}
+		ds1307->wakeirq = err;
+
+		err = dev_pm_set_dedicated_wake_irq(&client->dev,
+						    ds1307->wakeirq);
+		if (err) {
+			dev_err(&client->dev, "unable to setup wakeIRQ %d!\n",
+				err);
+			goto exit;
 		}
 	}
 
+no_irq:
 	if (chip->nvram_size) {
 
 		ds1307->nvram = devm_kzalloc(&client->dev,
@@ -1213,6 +1240,9 @@ static int ds1307_remove(struct i2c_client *client)
 {
 	struct ds1307 *ds1307 = i2c_get_clientdata(client);
 
+	if (ds1307->wakeirq)
+		dev_pm_clear_wake_irq(&client->dev);
+
 	if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags))
 		sysfs_remove_bin_file(&client->dev.kobj, ds1307->nvram);