power: supply: max17040: Add IRQ handler for low SOC alert

According datasheet max17040 has a pin for alert host for low SOC.
This pin can be used as external interrupt, so we need to check for
interrupts assigned for device and handle it.

In handler we are checking and storing fuel gauge registers values
and send an uevent to notificate user space, so user space can decide
save work or turn off since the alert demonstrate that the battery may
no have the power to keep the system turned on for much longer.
Signed-off-by: Matheus Castello <matheus@castello.eng.br>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/max17040_battery.c

@@ -13,6 +13,7 @@
 #include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/delay.h>
+#include <linux/interrupt.h>
 #include <linux/power_supply.h>
 #include <linux/max17040_battery.h>
 #include <linux/slab.h>
@@ -160,21 +161,54 @@ static void max17040_get_status(struct i2c_client *client)
 		chip->status = POWER_SUPPLY_STATUS_FULL;
 }
 
+static void max17040_check_changes(struct i2c_client *client)
+{
+	max17040_get_vcell(client);
+	max17040_get_soc(client);
+	max17040_get_online(client);
+	max17040_get_status(client);
+}
+
 static void max17040_work(struct work_struct *work)
 {
 	struct max17040_chip *chip;
 
 	chip = container_of(work, struct max17040_chip, work.work);
-
-	max17040_get_vcell(chip->client);
-	max17040_get_soc(chip->client);
-	max17040_get_online(chip->client);
-	max17040_get_status(chip->client);
+	max17040_check_changes(chip->client);
 
 	queue_delayed_work(system_power_efficient_wq, &chip->work,
 			   MAX17040_DELAY);
 }
 
+static irqreturn_t max17040_thread_handler(int id, void *dev)
+{
+	struct max17040_chip *chip = dev;
+	struct i2c_client *client = chip->client;
+
+	dev_warn(&client->dev, "IRQ: Alert battery low level");
+	/* read registers */
+	max17040_check_changes(chip->client);
+
+	/* send uevent */
+	power_supply_changed(chip->battery);
+
+	return IRQ_HANDLED;
+}
+
+static int max17040_enable_alert_irq(struct max17040_chip *chip)
+{
+	struct i2c_client *client = chip->client;
+	unsigned int flags;
+	int ret;
+
+	flags = IRQF_TRIGGER_FALLING | IRQF_ONESHOT;
+	ret = devm_request_threaded_irq(&client->dev, client->irq, NULL,
+					max17040_thread_handler, flags,
+					chip->battery->desc->name, chip);
+
+	return ret;
+}
+
 static enum power_supply_property max17040_battery_props[] = {
 	POWER_SUPPLY_PROP_STATUS,
 	POWER_SUPPLY_PROP_ONLINE,
@@ -220,6 +254,19 @@ static int max17040_probe(struct i2c_client *client,
 	max17040_reset(client);
 	max17040_get_version(client);
 
+	/* check interrupt */
+	if (client->irq && of_device_is_compatible(client->dev.of_node,
+						   "maxim,max77836-battery")) {
+		int ret;
+
+		ret = max17040_enable_alert_irq(chip);
+		if (ret) {
+			client->irq = 0;
+			dev_warn(&client->dev,
+				 "Failed to get IRQ err %d\n", ret);
+		}
+	}
+
 	INIT_DEFERRABLE_WORK(&chip->work, max17040_work);
 	queue_delayed_work(system_power_efficient_wq, &chip->work,
 			   MAX17040_DELAY);
@@ -244,6 +291,14 @@ static int max17040_suspend(struct device *dev)
 	struct max17040_chip *chip = i2c_get_clientdata(client);
 
 	cancel_delayed_work(&chip->work);
+
+	if (client->irq) {
+		if (device_may_wakeup(dev))
+			enable_irq_wake(client->irq);
+		else
+			disable_irq_wake(client->irq);
+	}
+
 	return 0;
 }
 
@@ -254,6 +309,14 @@ static int max17040_resume(struct device *dev)
 
 	queue_delayed_work(system_power_efficient_wq, &chip->work,
 			   MAX17040_DELAY);
+
+	if (client->irq) {
+		if (device_may_wakeup(dev))
+			disable_irq_wake(client->irq);
+		else
+			enable_irq_wake(client->irq);
+	}
+
 	return 0;
 }