power: supply: Add driver for Pegatron Chagall battery

The Pegatron Chagall is an Android tablet utilizing a customized Cypress
CG7153AM microcontroller (MCU) as its battery fuel gauge. It supports a
single-cell battery and features a dual-color charging LED.

Signed-off-by: Svyatoslav Ryhel <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/Kconfig

···
 	  Say Y here to enable support for power supply provided by
 	  Active-semi ActivePath ACT8945A charger.
 
+config BATTERY_CHAGALL
+	tristate "Pegatron Chagall battery driver"
+	depends on I2C
+	depends on LEDS_CLASS
+	help
+	  Say Y to include support for Cypress CG7153AM IC based battery
+	  fuel gauge with custom firmware found in Pegatron Chagall based
+	  tablet line.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called chagall-battery.
+
 config BATTERY_CPCAP
 	tristate "Motorola CPCAP PMIC battery driver"
 	depends on MFD_CPCAP && IIO

drivers/power/supply/Makefile

···
 obj-$(CONFIG_BATTERY_ACT8945A)	+= act8945a_charger.o
 obj-$(CONFIG_BATTERY_AXP20X)	+= axp20x_battery.o
 obj-$(CONFIG_CHARGER_AXP20X)	+= axp20x_ac_power.o
+obj-$(CONFIG_BATTERY_CHAGALL)	+= chagall-battery.o
 obj-$(CONFIG_BATTERY_CPCAP)	+= cpcap-battery.o
 obj-$(CONFIG_BATTERY_CW2015)	+= cw2015_battery.o
 obj-$(CONFIG_BATTERY_DS2760)	+= ds2760_battery.o

drivers/power/supply/chagall-battery.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/array_size.h>
+#include <linux/delay.h>
+#include <linux/devm-helpers.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/leds.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/power_supply.h>
+#include <linux/regmap.h>
+
+#define CHAGALL_REG_LED_AMBER				0x60
+#define CHAGALL_REG_LED_WHITE				0x70
+#define CHAGALL_REG_BATTERY_TEMPERATURE			0xa2
+#define CHAGALL_REG_BATTERY_VOLTAGE			0xa4
+#define CHAGALL_REG_BATTERY_CURRENT			0xa6
+#define CHAGALL_REG_BATTERY_CAPACITY			0xa8
+#define CHAGALL_REG_BATTERY_CHARGING_CURRENT		0xaa
+#define CHAGALL_REG_BATTERY_CHARGING_VOLTAGE		0xac
+#define CHAGALL_REG_BATTERY_STATUS			0xae
+#define   BATTERY_DISCHARGING				BIT(6)
+#define   BATTERY_FULL_CHARGED				BIT(5)
+#define   BATTERY_FULL_DISCHARGED			BIT(4)
+#define CHAGALL_REG_BATTERY_REMAIN_CAPACITY		0xb0
+#define CHAGALL_REG_BATTERY_FULL_CAPACITY		0xb2
+#define CHAGALL_REG_MAX_COUNT				0xb4
+
+#define CHAGALL_BATTERY_DATA_REFRESH			5000
+#define TEMP_CELSIUS_OFFSET				2731
+
+static const struct regmap_config chagall_battery_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = CHAGALL_REG_MAX_COUNT,
+	.reg_format_endian = REGMAP_ENDIAN_LITTLE,
+	.val_format_endian = REGMAP_ENDIAN_LITTLE,
+};
+
+struct chagall_battery_data {
+	struct regmap *regmap;
+	struct led_classdev amber_led;
+	struct led_classdev white_led;
+	struct power_supply *battery;
+	struct delayed_work poll_work;
+	u16 last_state;
+};
+
+static void chagall_led_set_brightness_amber(struct led_classdev *led,
+					     enum led_brightness brightness)
+{
+	struct chagall_battery_data *cg =
+		container_of(led, struct chagall_battery_data, amber_led);
+
+	regmap_write(cg->regmap, CHAGALL_REG_LED_AMBER, brightness);
+}
+
+static void chagall_led_set_brightness_white(struct led_classdev *led,
+					     enum led_brightness brightness)
+{
+	struct chagall_battery_data *cg =
+		container_of(led, struct chagall_battery_data, white_led);
+
+	regmap_write(cg->regmap, CHAGALL_REG_LED_WHITE, brightness);
+}
+
+static const enum power_supply_property chagall_battery_properties[] = {
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+	POWER_SUPPLY_PROP_VOLTAGE_MAX,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_CURRENT_MAX,
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_TEMP,
+	POWER_SUPPLY_PROP_CHARGE_FULL,
+	POWER_SUPPLY_PROP_CHARGE_NOW,
+};
+
+static const unsigned int chagall_battery_prop_offs[] = {
+	[POWER_SUPPLY_PROP_STATUS] = CHAGALL_REG_BATTERY_STATUS,
+	[POWER_SUPPLY_PROP_VOLTAGE_NOW] = CHAGALL_REG_BATTERY_VOLTAGE,
+	[POWER_SUPPLY_PROP_VOLTAGE_MAX] = CHAGALL_REG_BATTERY_CHARGING_VOLTAGE,
+	[POWER_SUPPLY_PROP_CURRENT_NOW] = CHAGALL_REG_BATTERY_CURRENT,
+	[POWER_SUPPLY_PROP_CURRENT_MAX] = CHAGALL_REG_BATTERY_CHARGING_CURRENT,
+	[POWER_SUPPLY_PROP_CAPACITY] = CHAGALL_REG_BATTERY_CAPACITY,
+	[POWER_SUPPLY_PROP_TEMP] = CHAGALL_REG_BATTERY_TEMPERATURE,
+	[POWER_SUPPLY_PROP_CHARGE_FULL] = CHAGALL_REG_BATTERY_FULL_CAPACITY,
+	[POWER_SUPPLY_PROP_CHARGE_NOW] = CHAGALL_REG_BATTERY_REMAIN_CAPACITY,
+};
+
+static int chagall_battery_get_value(struct chagall_battery_data *cg,
+				     enum power_supply_property psp, u32 *val)
+{
+	if (psp >= ARRAY_SIZE(chagall_battery_prop_offs))
+		return -EINVAL;
+	if (!chagall_battery_prop_offs[psp])
+		return -EINVAL;
+
+	/* Battery data is stored in 2 consecutive registers with little-endian */
+	return regmap_bulk_read(cg->regmap, chagall_battery_prop_offs[psp], val, 2);
+}
+
+static int chagall_battery_get_status(u32 status_reg)
+{
+	if (status_reg & BATTERY_FULL_CHARGED)
+		return POWER_SUPPLY_STATUS_FULL;
+	else if (status_reg & BATTERY_DISCHARGING)
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+	else
+		return POWER_SUPPLY_STATUS_CHARGING;
+}
+
+static int chagall_battery_get_property(struct power_supply *psy,
+					enum power_supply_property psp,
+					union power_supply_propval *val)
+{
+	struct chagall_battery_data *cg = power_supply_get_drvdata(psy);
+	int ret;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_PRESENT:
+		val->intval = 1;
+		break;
+
+	default:
+		ret = chagall_battery_get_value(cg, psp, &val->intval);
+		if (ret)
+			return ret;
+
+		switch (psp) {
+		case POWER_SUPPLY_PROP_TEMP:
+			val->intval -= TEMP_CELSIUS_OFFSET;
+			break;
+
+		case POWER_SUPPLY_PROP_VOLTAGE_MAX:
+		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		case POWER_SUPPLY_PROP_CURRENT_MAX:
+		case POWER_SUPPLY_PROP_CURRENT_NOW:
+		case POWER_SUPPLY_PROP_CHARGE_FULL:
+		case POWER_SUPPLY_PROP_CHARGE_NOW:
+			val->intval *= 1000;
+			break;
+
+		case POWER_SUPPLY_PROP_STATUS:
+			val->intval = chagall_battery_get_status(val->intval);
+			break;
+
+		default:
+			break;
+		}
+
+		break;
+	}
+
+	return 0;
+}
+
+static void chagall_battery_poll_work(struct work_struct *work)
+{
+	struct chagall_battery_data *cg =
+		container_of(work, struct chagall_battery_data, poll_work.work);
+	u32 state;
+	int ret;
+
+	ret = chagall_battery_get_value(cg, POWER_SUPPLY_PROP_STATUS, &state);
+	if (ret)
+		return;
+
+	state = chagall_battery_get_status(state);
+
+	if (cg->last_state != state) {
+		cg->last_state = state;
+		power_supply_changed(cg->battery);
+	}
+
+	/* continuously send uevent notification */
+	schedule_delayed_work(&cg->poll_work,
+			      msecs_to_jiffies(CHAGALL_BATTERY_DATA_REFRESH));
+}
+
+static const struct power_supply_desc chagall_battery_desc = {
+	.name = "chagall-battery",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = chagall_battery_properties,
+	.num_properties = ARRAY_SIZE(chagall_battery_properties),
+	.get_property = chagall_battery_get_property,
+	.external_power_changed = power_supply_changed,
+};
+
+static int chagall_battery_probe(struct i2c_client *client)
+{
+	struct chagall_battery_data *cg;
+	struct device *dev = &client->dev;
+	struct power_supply_config cfg = { };
+	int ret;
+
+	cg = devm_kzalloc(dev, sizeof(*cg), GFP_KERNEL);
+	if (!cg)
+		return -ENOMEM;
+
+	cfg.drv_data = cg;
+	cfg.fwnode = dev_fwnode(dev);
+
+	i2c_set_clientdata(client, cg);
+
+	cg->regmap = devm_regmap_init_i2c(client, &chagall_battery_regmap_config);
+	if (IS_ERR(cg->regmap))
+		return dev_err_probe(dev, PTR_ERR(cg->regmap), "cannot allocate regmap\n");
+
+	cg->last_state = POWER_SUPPLY_STATUS_UNKNOWN;
+	cg->battery = devm_power_supply_register(dev, &chagall_battery_desc, &cfg);
+	if (IS_ERR(cg->battery))
+		return dev_err_probe(dev, PTR_ERR(cg->battery),
+				     "failed to register power supply\n");
+
+	cg->amber_led.name = "power::amber";
+	cg->amber_led.max_brightness = 1;
+	cg->amber_led.flags = LED_CORE_SUSPENDRESUME;
+	cg->amber_led.brightness_set = chagall_led_set_brightness_amber;
+	cg->amber_led.default_trigger = "chagall-battery-charging";
+
+	ret = devm_led_classdev_register(dev, &cg->amber_led);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to register amber LED\n");
+
+	cg->white_led.name = "power::white";
+	cg->white_led.max_brightness = 1;
+	cg->white_led.flags = LED_CORE_SUSPENDRESUME;
+	cg->white_led.brightness_set = chagall_led_set_brightness_white;
+	cg->white_led.default_trigger = "chagall-battery-full";
+
+	ret = devm_led_classdev_register(dev, &cg->white_led);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to register white LED\n");
+
+	led_set_brightness(&cg->amber_led, LED_OFF);
+	led_set_brightness(&cg->white_led, LED_OFF);
+
+	ret = devm_delayed_work_autocancel(dev, &cg->poll_work, chagall_battery_poll_work);
+	if (ret)
+		return ret;
+
+	schedule_delayed_work(&cg->poll_work, msecs_to_jiffies(CHAGALL_BATTERY_DATA_REFRESH));
+
+	return 0;
+}
+
+static int __maybe_unused chagall_battery_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct chagall_battery_data *cg = i2c_get_clientdata(client);
+
+	cancel_delayed_work_sync(&cg->poll_work);
+
+	return 0;
+}
+
+static int __maybe_unused chagall_battery_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct chagall_battery_data *cg = i2c_get_clientdata(client);
+
+	schedule_delayed_work(&cg->poll_work, msecs_to_jiffies(CHAGALL_BATTERY_DATA_REFRESH));
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(chagall_battery_pm_ops,
+			 chagall_battery_suspend, chagall_battery_resume);
+
+static const struct of_device_id chagall_of_match[] = {
+	{ .compatible = "pegatron,chagall-ec" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, chagall_of_match);
+
+static struct i2c_driver chagall_battery_driver = {
+	.driver = {
+		.name = "chagall-battery",
+		.pm = &chagall_battery_pm_ops,
+		.of_match_table = chagall_of_match,
+	},
+	.probe = chagall_battery_probe,
+};
+module_i2c_driver(chagall_battery_driver);
+
+MODULE_AUTHOR("Svyatoslav Ryhel <[e-mail]>");
+MODULE_DESCRIPTION("Pegatron Chagall fuel gauge driver");
+MODULE_LICENSE("GPL");