power_supply: wilco_ec: Add charging config driver

Add a driver to control the charging algorithm used on Wilco
devices. See Documentation/ABI/testing/sysfs-class-power-wilco
for the userspace interface and other info.
Signed-off-by: Nick Crews <ncrews@chromium.org>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/ABI/testing/sysfs-class-power-wilco

+What:		/sys/class/power_supply/wilco-charger/charge_type
+Date:		April 2019
+KernelVersion:	5.2
+Description:
+		What charging algorithm to use:
+
+		Standard: Fully charges battery at a standard rate.
+		Adaptive: Battery settings adaptively optimized based on
+			typical battery usage pattern.
+		Fast: Battery charges over a shorter period.
+		Trickle: Extends battery lifespan, intended for users who
+			primarily use their Chromebook while connected to AC.
+		Custom: A low and high threshold percentage is specified.
+			Charging begins when level drops below
+			charge_control_start_threshold, and ceases when
+			level is above charge_control_end_threshold.
+
+What:		/sys/class/power_supply/wilco-charger/charge_control_start_threshold
+Date:		April 2019
+KernelVersion:	5.2
+Description:
+		Used when charge_type="Custom", as described above. Measured in
+		percentages. The valid range is [50, 95].
+
+What:		/sys/class/power_supply/wilco-charger/charge_control_end_threshold
+Date:		April 2019
+KernelVersion:	5.2
+Description:
+		Used when charge_type="Custom", as described above. Measured in
+		percentages. The valid range is [55, 100].

drivers/power/supply/Kconfig

@@ -702,4 +702,13 @@ config CHARGER_UCS1002
 	  Say Y to enable support for Microchip UCS1002 Programmable
 	  USB Port Power Controller with Charger Emulation.
 
+config CHARGER_WILCO
+	tristate "Wilco EC based charger for ChromeOS"
+	depends on WILCO_EC
+	help
+	  Say Y here to enable control of the charging routines performed
+	  by the Embedded Controller on the Chromebook named Wilco. Further
+	  information can be found in
+	  Documentation/ABI/testing/sysfs-class-power-wilco
+
 endif # POWER_SUPPLY

drivers/power/supply/Makefile

@@ -91,3 +91,4 @@ obj-$(CONFIG_CHARGER_CROS_USBPD)	+= cros_usbpd-charger.o
 obj-$(CONFIG_CHARGER_SC2731)	+= sc2731_charger.o
 obj-$(CONFIG_FUEL_GAUGE_SC27XX)	+= sc27xx_fuel_gauge.o
 obj-$(CONFIG_CHARGER_UCS1002)	+= ucs1002_power.o
+obj-$(CONFIG_CHARGER_WILCO)	+= wilco-charger.o

drivers/power/supply/wilco-charger.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Charging control driver for the Wilco EC
+ *
+ * Copyright 2019 Google LLC
+ *
+ * See Documentation/ABI/testing/sysfs-class-power and
+ * Documentation/ABI/testing/sysfs-class-power-wilco for userspace interface
+ * and other info.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/platform_data/wilco-ec.h>
+#include <linux/power_supply.h>
+
+#define DRV_NAME "wilco-charger"
+
+/* Property IDs and related EC constants */
+#define PID_CHARGE_MODE		0x0710
+#define PID_CHARGE_LOWER_LIMIT	0x0711
+#define PID_CHARGE_UPPER_LIMIT	0x0712
+
+enum charge_mode {
+	CHARGE_MODE_STD = 1,	/* Used for Standard */
+	CHARGE_MODE_EXP = 2,	/* Express Charge, used for Fast */
+	CHARGE_MODE_AC = 3,	/* Mostly AC use, used for Trickle */
+	CHARGE_MODE_AUTO = 4,	/* Used for Adaptive */
+	CHARGE_MODE_CUSTOM = 5,	/* Used for Custom */
+};
+
+#define CHARGE_LOWER_LIMIT_MIN	50
+#define CHARGE_LOWER_LIMIT_MAX	95
+#define CHARGE_UPPER_LIMIT_MIN	55
+#define CHARGE_UPPER_LIMIT_MAX	100
+
+/* Convert from POWER_SUPPLY_PROP_CHARGE_TYPE value to the EC's charge mode */
+static int psp_val_to_charge_mode(int psp_val)
+{
+	switch (psp_val) {
+	case POWER_SUPPLY_CHARGE_TYPE_TRICKLE:
+		return CHARGE_MODE_AC;
+	case POWER_SUPPLY_CHARGE_TYPE_FAST:
+		return CHARGE_MODE_EXP;
+	case POWER_SUPPLY_CHARGE_TYPE_STANDARD:
+		return CHARGE_MODE_STD;
+	case POWER_SUPPLY_CHARGE_TYPE_ADAPTIVE:
+		return CHARGE_MODE_AUTO;
+	case POWER_SUPPLY_CHARGE_TYPE_CUSTOM:
+		return CHARGE_MODE_CUSTOM;
+	default:
+		return -EINVAL;
+	}
+}
+
+/* Convert from EC's charge mode to POWER_SUPPLY_PROP_CHARGE_TYPE value */
+static int charge_mode_to_psp_val(enum charge_mode mode)
+{
+	switch (mode) {
+	case CHARGE_MODE_AC:
+		return POWER_SUPPLY_CHARGE_TYPE_TRICKLE;
+	case CHARGE_MODE_EXP:
+		return POWER_SUPPLY_CHARGE_TYPE_FAST;
+	case CHARGE_MODE_STD:
+		return POWER_SUPPLY_CHARGE_TYPE_STANDARD;
+	case CHARGE_MODE_AUTO:
+		return POWER_SUPPLY_CHARGE_TYPE_ADAPTIVE;
+	case CHARGE_MODE_CUSTOM:
+		return POWER_SUPPLY_CHARGE_TYPE_CUSTOM;
+	default:
+		return -EINVAL;
+	}
+}
+
+static enum power_supply_property wilco_charge_props[] = {
+	POWER_SUPPLY_PROP_CHARGE_TYPE,
+	POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD,
+	POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD,
+};
+
+static int wilco_charge_get_property(struct power_supply *psy,
+				     enum power_supply_property psp,
+				     union power_supply_propval *val)
+{
+	struct wilco_ec_device *ec = power_supply_get_drvdata(psy);
+	u32 property_id;
+	int ret;
+	u8 raw;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_TYPE:
+		property_id = PID_CHARGE_MODE;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD:
+		property_id = PID_CHARGE_LOWER_LIMIT;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
+		property_id = PID_CHARGE_UPPER_LIMIT;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	ret = wilco_ec_get_byte_property(ec, property_id, &raw);
+	if (ret < 0)
+		return ret;
+	if (property_id == PID_CHARGE_MODE) {
+		ret = charge_mode_to_psp_val(raw);
+		if (ret < 0)
+			return -EBADMSG;
+		raw = ret;
+	}
+	val->intval = raw;
+
+	return 0;
+}
+
+static int wilco_charge_set_property(struct power_supply *psy,
+				     enum power_supply_property psp,
+				     const union power_supply_propval *val)
+{
+	struct wilco_ec_device *ec = power_supply_get_drvdata(psy);
+	int mode;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_TYPE:
+		mode = psp_val_to_charge_mode(val->intval);
+		if (mode < 0)
+			return -EINVAL;
+		return wilco_ec_set_byte_property(ec, PID_CHARGE_MODE, mode);
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD:
+		if (val->intval < CHARGE_LOWER_LIMIT_MIN ||
+		    val->intval > CHARGE_LOWER_LIMIT_MAX)
+			return -EINVAL;
+		return wilco_ec_set_byte_property(ec, PID_CHARGE_LOWER_LIMIT,
+						  val->intval);
+	case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
+		if (val->intval < CHARGE_UPPER_LIMIT_MIN ||
+		    val->intval > CHARGE_UPPER_LIMIT_MAX)
+			return -EINVAL;
+		return wilco_ec_set_byte_property(ec, PID_CHARGE_UPPER_LIMIT,
+						  val->intval);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int wilco_charge_property_is_writeable(struct power_supply *psy,
+					      enum power_supply_property psp)
+{
+	return 1;
+}
+
+static const struct power_supply_desc wilco_ps_desc = {
+	.properties		= wilco_charge_props,
+	.num_properties		= ARRAY_SIZE(wilco_charge_props),
+	.get_property		= wilco_charge_get_property,
+	.set_property		= wilco_charge_set_property,
+	.property_is_writeable	= wilco_charge_property_is_writeable,
+	.name			= DRV_NAME,
+	.type			= POWER_SUPPLY_TYPE_MAINS,
+};
+
+static int wilco_charge_probe(struct platform_device *pdev)
+{
+	struct wilco_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
+	struct power_supply_config psy_cfg = {};
+	struct power_supply *psy;
+
+	psy_cfg.drv_data = ec;
+	psy = devm_power_supply_register(&pdev->dev, &wilco_ps_desc, &psy_cfg);
+
+	return PTR_ERR_OR_ZERO(psy);
+}
+
+static struct platform_driver wilco_charge_driver = {
+	.probe	= wilco_charge_probe,
+	.driver = {
+		.name = DRV_NAME,
+	}
+};
+module_platform_driver(wilco_charge_driver);
+
+MODULE_ALIAS("platform:" DRV_NAME);
+MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Wilco EC charge control driver");