power: supply: max8997_charger: Set CHARGER current limit

Register for extcon notification and set charging current depending on
the detected cable type. Current values are taken from vendor kernel,
where most charger types end up setting 650mA [0].

Also enable and disable the CHARGER regulator based on extcon events.

[0] https://github.com/krzk/linux-vendor-backup/blob/samsung/galaxy-s2-epic-4g-touch-sph-d710-exynos4210-dump/drivers/misc/max8997-muic.c#L1675-L1678

Signed-off-by: Timon Baetz <timon.baetz@protonmail.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/Kconfig

@@ -546,6 +546,7 @@ config CHARGER_MAX77693
 config CHARGER_MAX8997
 	tristate "Maxim MAX8997/MAX8966 PMIC battery charger driver"
 	depends on MFD_MAX8997 && REGULATOR_MAX8997
+	depends on EXTCON || !EXTCON
 	help
 	  Say Y to enable support for the battery charger control sysfs and
 	  platform data of MAX8997/LP3974 PMICs.

drivers/power/supply/max8997_charger.c

@@ -6,12 +6,14 @@
 //  MyungJoo Ham <myungjoo.ham@samsung.com>
 
 #include <linux/err.h>
+#include <linux/extcon.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/platform_device.h>
 #include <linux/power_supply.h>
 #include <linux/mfd/max8997.h>
 #include <linux/mfd/max8997-private.h>
+#include <linux/regulator/consumer.h>
 
 /* MAX8997_REG_STATUS4 */
 #define DCINOK_SHIFT		1
@@ -31,6 +33,10 @@ struct charger_data {
 	struct device *dev;
 	struct max8997_dev *iodev;
 	struct power_supply *battery;
+	struct regulator *reg;
+	struct extcon_dev *edev;
+	struct notifier_block extcon_nb;
+	struct work_struct extcon_work;
 };
 
 static enum power_supply_property max8997_battery_props[] = {
@@ -88,6 +94,67 @@ static int max8997_battery_get_property(struct power_supply *psy,
 	return 0;
 }
 
+static void max8997_battery_extcon_evt_stop_work(void *data)
+{
+	struct charger_data *charger = data;
+
+	cancel_work_sync(&charger->extcon_work);
+}
+
+static void max8997_battery_extcon_evt_worker(struct work_struct *work)
+{
+	struct charger_data *charger =
+	    container_of(work, struct charger_data, extcon_work);
+	struct extcon_dev *edev = charger->edev;
+	int current_limit;
+
+	if (extcon_get_state(edev, EXTCON_CHG_USB_SDP) > 0) {
+		dev_dbg(charger->dev, "USB SDP charger is connected\n");
+		current_limit = 450000;
+	} else if (extcon_get_state(edev, EXTCON_CHG_USB_DCP) > 0) {
+		dev_dbg(charger->dev, "USB DCP charger is connected\n");
+		current_limit = 650000;
+	} else if (extcon_get_state(edev, EXTCON_CHG_USB_FAST) > 0) {
+		dev_dbg(charger->dev, "USB FAST charger is connected\n");
+		current_limit = 650000;
+	} else if (extcon_get_state(edev, EXTCON_CHG_USB_SLOW) > 0) {
+		dev_dbg(charger->dev, "USB SLOW charger is connected\n");
+		current_limit = 650000;
+	} else if (extcon_get_state(edev, EXTCON_CHG_USB_CDP) > 0) {
+		dev_dbg(charger->dev, "USB CDP charger is connected\n");
+		current_limit = 650000;
+	} else {
+		dev_dbg(charger->dev, "USB charger is diconnected\n");
+		current_limit = -1;
+	}
+
+	if (current_limit > 0) {
+		int ret = regulator_set_current_limit(charger->reg, current_limit, current_limit);
+
+		if (ret) {
+			dev_err(charger->dev, "failed to set current limit: %d\n", ret);
+			return;
+		}
+		ret = regulator_enable(charger->reg);
+		if (ret)
+			dev_err(charger->dev, "failed to enable regulator: %d\n", ret);
+	} else {
+		int ret  = regulator_disable(charger->reg);
+
+		if (ret)
+			dev_err(charger->dev, "failed to disable regulator: %d\n", ret);
+	}
+}
+
+static int max8997_battery_extcon_evt(struct notifier_block *nb,
+				unsigned long event, void *param)
+{
+	struct charger_data *charger =
+		container_of(nb, struct charger_data, extcon_nb);
+	schedule_work(&charger->extcon_work);
+	return NOTIFY_OK;
+}
+
 static const struct power_supply_desc max8997_battery_desc = {
 	.name		= "max8997_pmic",
 	.type		= POWER_SUPPLY_TYPE_BATTERY,
@@ -170,6 +237,35 @@ static int max8997_battery_probe(struct platform_device *pdev)
 		return PTR_ERR(charger->battery);
 	}
 
+	charger->reg = devm_regulator_get_optional(&pdev->dev, "charger");
+	if (IS_ERR(charger->reg)) {
+		if (PTR_ERR(charger->reg) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		dev_info(&pdev->dev, "couldn't get charger regulator\n");
+	}
+	charger->edev = extcon_get_edev_by_phandle(&pdev->dev, 0);
+	if (IS_ERR(charger->edev)) {
+		if (PTR_ERR(charger->edev) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		dev_info(charger->dev, "couldn't get extcon device\n");
+	}
+
+	if (!IS_ERR(charger->reg) && !IS_ERR(charger->edev)) {
+		INIT_WORK(&charger->extcon_work, max8997_battery_extcon_evt_worker);
+		ret = devm_add_action(&pdev->dev, max8997_battery_extcon_evt_stop_work, charger);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to add extcon evt stop action: %d\n", ret);
+			return ret;
+		}
+		charger->extcon_nb.notifier_call = max8997_battery_extcon_evt;
+		ret = devm_extcon_register_notifier_all(&pdev->dev, charger->edev,
+							&charger->extcon_nb);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to register extcon notifier\n");
+			return ret;
+		};
+	}
+
 	return 0;
 }