[PATCH v3 6/8] power: supply: rt5033_charger: Add cable detection and USB OTG supply

[Jakob Hauser <jahau@rocketmail.com>]

Implement cable detection by extcon and handle the driver according to the
connector type.

There are basically three types of action: "set_charging", "set_otg" and
"set_disconnect".

A forth helper function to "unset_otg" was added because this is used in both
"set_charging" and "set_disconnect". In the first case it covers the rather
rare event that someone changes from OTG to charging without disconnect. In
the second case, when disconnecting, the values are set back to the ones from
initialization to return into a defined state.

Additionally, there is "set_mivr". When connecting to e.g. a laptop/PC, the
minimum input voltage regulation (MIVR) shall prevent a voltage drop if the
cable or the supply is weak. The MIVR value is set to 4600MV, same as in the
Android driver [1]. When disconnecting, MIVR is set back to DISABLED.

In the function rt5033_get_charger_state(): When in OTG mode, the chip
reports status "charging". Change this to "discharging" because there is
no charging going on in OTG mode [2].

[1] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/battery/rt5033_charger.c#L499
[2] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/battery/rt5033_charger.c#L686-L687

Tested-by: Raymond Hackley <raymondhackley@protonmail.com>
Signed-off-by: Jakob Hauser <jahau@rocketmail.com>
---
 drivers/power/supply/rt5033_charger.c | 265 +++++++++++++++++++++++++-
 include/linux/mfd/rt5033.h            |   8 +
 2 files changed, 271 insertions(+), 2 deletions(-)

diff --git a/drivers/power/supply/rt5033_charger.c b/drivers/power/supply/rt5033_charger.c
index 038530d2f0a0..94f7b8e0da42 100644
--- a/drivers/power/supply/rt5033_charger.c
+++ b/drivers/power/supply/rt5033_charger.c
@@ -10,7 +10,10 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/devm-helpers.h>
+#include <linux/extcon.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
 #include <linux/power_supply.h>
 #include <linux/mfd/rt5033-private.h>
@@ -44,6 +47,10 @@ static int rt5033_get_charger_state(struct rt5033_charger *charger)
 		state = POWER_SUPPLY_STATUS_UNKNOWN;
 	}
 
+	/* For OTG mode, RT5033 would still report "charging" */
+	if (charger->otg)
+		state = POWER_SUPPLY_STATUS_DISCHARGING;
+
 	return state;
 }
 
@@ -135,6 +142,9 @@ static inline int rt5033_init_const_charge(struct rt5033_charger *charger)
 		return -EINVAL;
 	}
 
+	/* Store that value for later usage */
+	charger->cv_regval = reg_data;
+
 	/* Set end of charge current */
 	if (chg->eoc_uamp < RT5033_CHARGER_EOC_MIN ||
 	    chg->eoc_uamp > RT5033_CHARGER_EOC_MAX) {
@@ -318,6 +328,152 @@ static int rt5033_charger_reg_init(struct rt5033_charger *charger)
 	return 0;
 }
 
+static int rt5033_charger_set_otg(struct rt5033_charger *charger)
+{
+	int ret;
+
+	mutex_lock(&charger->lock);
+
+	/* Set OTG boost v_out to 5 volts */
+	ret = regmap_update_bits(charger->rt5033->regmap, RT5033_REG_CHG_CTRL2,
+			RT5033_CHGCTRL2_CV_MASK,
+			0x37 << RT5033_CHGCTRL2_CV_SHIFT);
+	if (ret) {
+		dev_err(charger->dev, "Failed set OTG boost v_out\n");
+		return -EINVAL;
+	}
+
+	/* Set operation mode to OTG */
+	ret = regmap_update_bits(charger->rt5033->regmap, RT5033_REG_CHG_CTRL1,
+			RT5033_CHGCTRL1_MODE_MASK, RT5033_BOOST_MODE);
+	if (ret) {
+		dev_err(charger->dev, "Failed to update OTG mode.\n");
+		return -EINVAL;
+	}
+
+	/* In case someone switched from charging to OTG directly */
+	if (charger->online)
+		charger->online = false;
+
+	charger->otg = true;
+
+	mutex_unlock(&charger->lock);
+
+	return 0;
+}
+
+static int rt5033_charger_unset_otg(struct rt5033_charger *charger)
+{
+	int ret;
+	u8 data;
+
+	/* Restore constant voltage for charging */
+	data = charger->cv_regval;
+	ret = regmap_update_bits(charger->rt5033->regmap, RT5033_REG_CHG_CTRL2,
+			RT5033_CHGCTRL2_CV_MASK,
+			data << RT5033_CHGCTRL2_CV_SHIFT);
+	if (ret) {
+		dev_err(charger->dev, "Failed to restore constant voltage\n");
+		return -EINVAL;
+	}
+
+	/* Set operation mode to charging */
+	ret = regmap_update_bits(charger->rt5033->regmap, RT5033_REG_CHG_CTRL1,
+			RT5033_CHGCTRL1_MODE_MASK, RT5033_CHARGER_MODE);
+	if (ret) {
+		dev_err(charger->dev, "Failed to update charger mode.\n");
+		return -EINVAL;
+	}
+
+	charger->otg = false;
+
+	return 0;
+}
+
+static int rt5033_charger_set_charging(struct rt5033_charger *charger)
+{
+	int ret;
+
+	mutex_lock(&charger->lock);
+
+	/* In case someone switched from OTG to charging directly */
+	if (charger->otg) {
+		ret = rt5033_charger_unset_otg(charger);
+		if (ret)
+			return -EINVAL;
+	}
+
+	charger->online = true;
+
+	mutex_unlock(&charger->lock);
+
+	return 0;
+}
+
+static int rt5033_charger_set_mivr(struct rt5033_charger *charger)
+{
+	int ret;
+
+	mutex_lock(&charger->lock);
+
+	/*
+	 * When connected via USB connector type SDP (Standard Downstream Port),
+	 * the minimum input voltage regulation (MIVR) should be enabled. It
+	 * prevents an input voltage drop due to insufficient current provided
+	 * by the adapter or USB input. As a downside, it may reduces the
+	 * charging current and thus slows the charging.
+	 */
+	ret = regmap_update_bits(charger->rt5033->regmap, RT5033_REG_CHG_CTRL4,
+			RT5033_CHGCTRL4_MIVR_MASK, RT5033_CHARGER_MIVR_4600MV);
+	if (ret) {
+		dev_err(charger->dev, "Failed to set MIVR level.\n");
+		return -EINVAL;
+	}
+
+	charger->mivr_enabled = true;
+
+	mutex_unlock(&charger->lock);
+
+	/* Beyond this, do the same steps like setting charging */
+	rt5033_charger_set_charging(charger);
+
+	return 0;
+}
+
+static int rt5033_charger_set_disconnect(struct rt5033_charger *charger)
+{
+	int ret;
+
+	mutex_lock(&charger->lock);
+
+	/* Disable MIVR if enabled */
+	if (charger->mivr_enabled) {
+		ret = regmap_update_bits(charger->rt5033->regmap,
+				RT5033_REG_CHG_CTRL4,
+				RT5033_CHGCTRL4_MIVR_MASK,
+				RT5033_CHARGER_MIVR_DISABLE);
+		if (ret) {
+			dev_err(charger->dev, "Failed to disable MIVR.\n");
+			return -EINVAL;
+		}
+
+		charger->mivr_enabled = false;
+	}
+
+	if (charger->otg) {
+		ret = rt5033_charger_unset_otg(charger);
+		if (ret)
+			return -EINVAL;
+	}
+
+	if (charger->online)
+		charger->online = false;
+
+	mutex_unlock(&charger->lock);
+
+	return 0;
+}
+
 static enum power_supply_property rt5033_charger_props[] = {
 	POWER_SUPPLY_PROP_STATUS,
 	POWER_SUPPLY_PROP_CHARGE_TYPE,
@@ -355,8 +511,7 @@ static int rt5033_charger_get_property(struct power_supply *psy,
 		val->strval = RT5033_MANUFACTURER;
 		break;
 	case POWER_SUPPLY_PROP_ONLINE:
-		val->intval = (rt5033_get_charger_state(charger) ==
-				POWER_SUPPLY_STATUS_CHARGING);
+		val->intval = charger->online;
 		break;
 	default:
 		return -EINVAL;
@@ -392,6 +547,86 @@ static struct rt5033_charger_data *rt5033_charger_dt_init(
 	return chg;
 }
 
+static void rt5033_charger_extcon_work(struct work_struct *work)
+{
+	struct rt5033_charger *charger =
+		container_of(work, struct rt5033_charger, extcon_work);
+	struct extcon_dev *edev = charger->edev;
+	int connector, state;
+	int ret;
+
+	for (connector = EXTCON_USB_HOST; connector <= EXTCON_CHG_USB_PD;
+	     connector++) {
+		state = extcon_get_state(edev, connector);
+		if (state == 1)
+			break;
+	}
+
+	/*
+	 * Adding a delay between extcon notification and extcon action. This
+	 * makes extcon action execution more reliable. Without the delay the
+	 * execution sometimes fails, possibly because the chip is busy or not
+	 * ready.
+	 */
+	msleep(100);
+
+	switch (connector) {
+	case EXTCON_CHG_USB_SDP:
+		ret = rt5033_charger_set_mivr(charger);
+		if (ret) {
+			dev_err(charger->dev, "failed to set USB mode\n");
+			break;
+		}
+		dev_info(charger->dev, "USB mode. connector type: %d\n",
+			 connector);
+		break;
+	case EXTCON_CHG_USB_DCP:
+	case EXTCON_CHG_USB_CDP:
+	case EXTCON_CHG_USB_ACA:
+	case EXTCON_CHG_USB_FAST:
+	case EXTCON_CHG_USB_SLOW:
+	case EXTCON_CHG_WPT:
+	case EXTCON_CHG_USB_PD:
+		ret = rt5033_charger_set_charging(charger);
+		if (ret) {
+			dev_err(charger->dev, "failed to set charging\n");
+			break;
+		}
+		dev_info(charger->dev, "charging. connector type: %d\n",
+			 connector);
+		break;
+	case EXTCON_USB_HOST:
+		ret = rt5033_charger_set_otg(charger);
+		if (ret) {
+			dev_err(charger->dev, "failed to set OTG\n");
+			break;
+		}
+		dev_info(charger->dev, "OTG enabled\n");
+		break;
+	default:
+		ret = rt5033_charger_set_disconnect(charger);
+		if (ret) {
+			dev_err(charger->dev, "failed to set disconnect\n");
+			break;
+		}
+		dev_info(charger->dev, "disconnected\n");
+		break;
+	}
+
+	power_supply_changed(charger->psy);
+}
+
+static int rt5033_charger_extcon_notifier(struct notifier_block *nb,
+					  unsigned long event, void *param)
+{
+	struct rt5033_charger *charger =
+		container_of(nb, struct rt5033_charger, extcon_nb);
+
+	schedule_work(&charger->extcon_work);
+
+	return NOTIFY_OK;
+}
+
 static const struct power_supply_desc rt5033_charger_desc = {
 	.name = "rt5033-charger",
 	.type = POWER_SUPPLY_TYPE_USB,
@@ -414,6 +649,7 @@ static int rt5033_charger_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, charger);
 	charger->dev = &pdev->dev;
 	charger->rt5033 = rt5033;
+	mutex_init(&charger->lock);
 
 	psy_cfg.of_node = pdev->dev.of_node;
 	psy_cfg.drv_data = charger;
@@ -434,6 +670,31 @@ static int rt5033_charger_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	/*
+	 * Extcon support is not vital for the charger to work. If no extcon
+	 * is available, just emit a warning and leave the probe function.
+	 */
+	charger->edev = extcon_get_edev_by_phandle(&pdev->dev, 0);
+	if (IS_ERR(charger->edev)) {
+		dev_warn(&pdev->dev, "no extcon phandle found in device-tree\n");
+		goto out;
+	}
+
+	ret = devm_work_autocancel(&pdev->dev, &charger->extcon_work,
+				   rt5033_charger_extcon_work);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to initialize extcon work\n");
+		return ret;
+	}
+
+	charger->extcon_nb.notifier_call = rt5033_charger_extcon_notifier;
+	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;
+	}
+out:
 	return 0;
 }
 
diff --git a/include/linux/mfd/rt5033.h b/include/linux/mfd/rt5033.h
index e99e2ab0c1c1..d2c613764756 100644
--- a/include/linux/mfd/rt5033.h
+++ b/include/linux/mfd/rt5033.h
@@ -53,6 +53,14 @@ struct rt5033_charger {
 	struct rt5033_dev		*rt5033;
 	struct power_supply		*psy;
 	struct rt5033_charger_data	*chg;
+	struct extcon_dev		*edev;
+	struct notifier_block		extcon_nb;
+	struct work_struct		extcon_work;
+	struct mutex			lock;
+	bool online;
+	bool otg;
+	bool mivr_enabled;
+	u8 cv_regval;
 };
 
 #endif /* __RT5033_H__ */
-- 
2.39.2