power: supply: Introduce MM8013 fuel gauge driver

Add a driver for the Mitsumi MM8013 fuel gauge. The driver is a vastly
cleaned up and improved version of the one that shipped in some obscure
Lenovo downstream kernel [1], with some register definitions borrowed from
ChromeOS EC platform code [2].

[1] https://github.com/adazem009/kernel_lenovo_bengal/commit/b6b346427a871715709bd22aae449b9383f3b66b
[2] https://chromium.googlesource.com/chromiumos/platform/ec/+/master/driver/battery/mm8013.h

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230621-topic-mm8013-v4-3-975aecd173ed@linaro.org
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

MAINTAINERS

@@ -14376,6 +14376,11 @@ W:	https://linuxtv.org
 T:	git git://linuxtv.org/media_tree.git
 F:	drivers/media/radio/radio-miropcm20*
 
+MITSUMI MM8013 FG DRIVER
+M:	Konrad Dybcio <konradybcio@kernel.org>
+F:	Documentation/devicetree/bindings/power/supply/mitsumi,mm8013.yaml
+F:	drivers/power/supply/mm8013.c
+
 MMP SUPPORT
 R:	Lubomir Rintel <lkundrak@v3.sk>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)

drivers/power/supply/Kconfig

@@ -951,4 +951,13 @@ config CHARGER_QCOM_SMB2
 	  adds support for the SMB2 switch mode battery charger found
 	  in PMI8998 and related PMICs.
 
+config FUEL_GAUGE_MM8013
+	tristate "Mitsumi MM8013 fuel gauge driver"
+	depends on I2C
+	help
+	  Say Y here to enable the Mitsumi MM8013 fuel gauge driver.
+	  It enables the monitoring of many battery parameters, including
+	  the state of charge, temperature, cycle count, actual and design
+	  capacity, etc.
+
 endif # POWER_SUPPLY

drivers/power/supply/Makefile

@@ -111,3 +111,4 @@ obj-$(CONFIG_BATTERY_SURFACE)	+= surface_battery.o
 obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
 obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
 obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_pmi8998_charger.o
+obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o

drivers/power/supply/mm8013.c

@@ -0,0 +1,274 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2016-2019 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2023, Linaro Limited
+ */
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/power_supply.h>
+#include <linux/regmap.h>
+
+#define REG_BATID			0x00 /* This one is very unclear */
+ #define BATID_101			0x0101 /* 107kOhm */
+ #define BATID_102			0x0102 /* 10kOhm */
+#define REG_TEMPERATURE			0x06
+#define REG_VOLTAGE			0x08
+#define REG_FLAGS			0x0a
+ #define MM8013_FLAG_OTC		BIT(15)
+ #define MM8013_FLAG_OTD		BIT(14)
+ #define MM8013_FLAG_BATHI		BIT(13)
+ #define MM8013_FLAG_FC			BIT(9)
+ #define MM8013_FLAG_CHG		BIT(8)
+ #define MM8013_FLAG_DSG		BIT(0)
+#define REG_FULL_CHARGE_CAPACITY	0x0e
+#define REG_AVERAGE_CURRENT		0x14
+#define REG_AVERAGE_TIME_TO_EMPTY	0x16
+#define REG_AVERAGE_TIME_TO_FULL	0x18
+#define REG_CYCLE_COUNT			0x2a
+#define REG_STATE_OF_CHARGE		0x2c
+#define REG_DESIGN_CAPACITY		0x3c
+/* TODO: 0x62-0x68 seem to contain 'MM8013C' in a length-prefixed, non-terminated string */
+
+#define DECIKELVIN_TO_DECIDEGC(t)	(t - 2731)
+
+struct mm8013_chip {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+static int mm8013_checkdevice(struct mm8013_chip *chip)
+{
+	int battery_id, ret;
+	u32 val;
+
+	ret = regmap_write(chip->regmap, REG_BATID, 0x0008);
+	if (ret < 0)
+		return ret;
+
+	regmap_read(chip->regmap, REG_BATID, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val == BATID_102)
+		battery_id = 2;
+	else if (val == BATID_101)
+		battery_id = 1;
+	else
+		return -EINVAL;
+
+	dev_dbg(&chip->client->dev, "battery_id: %d\n", battery_id);
+
+	return 0;
+}
+
+static enum power_supply_property mm8013_battery_props[] = {
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_CHARGE_FULL,
+	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_CYCLE_COUNT,
+	POWER_SUPPLY_PROP_HEALTH,
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_STATUS,
+	POWER_SUPPLY_PROP_TEMP,
+	POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG,
+	POWER_SUPPLY_PROP_TIME_TO_FULL_AVG,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+};
+
+static int mm8013_get_property(struct power_supply *psy,
+			       enum power_supply_property psp,
+			       union power_supply_propval *val)
+{
+	struct mm8013_chip *chip = psy->drv_data;
+	int ret = 0;
+	u32 regval;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CAPACITY:
+		ret = regmap_read(chip->regmap, REG_STATE_OF_CHARGE, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = regval;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+		ret = regmap_read(chip->regmap, REG_FULL_CHARGE_CAPACITY, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = 1000 * regval;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+		ret = regmap_read(chip->regmap, REG_DESIGN_CAPACITY, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = 1000 * regval;
+		break;
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		ret = regmap_read(chip->regmap, REG_AVERAGE_CURRENT, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = -1000 * (s16)regval;
+		break;
+	case POWER_SUPPLY_PROP_CYCLE_COUNT:
+		ret = regmap_read(chip->regmap, REG_CYCLE_COUNT, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = regval;
+		break;
+	case POWER_SUPPLY_PROP_HEALTH:
+		ret = regmap_read(chip->regmap, REG_FLAGS, &regval);
+		if (ret < 0)
+			return ret;
+
+		if (regval & MM8013_FLAG_BATHI)
+			val->intval = POWER_SUPPLY_HEALTH_OVERVOLTAGE;
+		else if (regval & (MM8013_FLAG_OTD | MM8013_FLAG_OTC))
+			val->intval = POWER_SUPPLY_HEALTH_OVERHEAT;
+		else
+			val->intval = POWER_SUPPLY_HEALTH_GOOD;
+		break;
+	case POWER_SUPPLY_PROP_PRESENT:
+		ret = regmap_read(chip->regmap, REG_TEMPERATURE, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = ((s16)regval > 0);
+		break;
+	case POWER_SUPPLY_PROP_STATUS:
+		ret = regmap_read(chip->regmap, REG_FLAGS, &regval);
+		if (ret < 0)
+			return ret;
+
+		if (regval & MM8013_FLAG_DSG)
+			val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+		else if (regval & MM8013_FLAG_CHG)
+			val->intval = POWER_SUPPLY_STATUS_CHARGING;
+		else if (regval & MM8013_FLAG_FC)
+			val->intval = POWER_SUPPLY_STATUS_FULL;
+		else
+			val->intval = POWER_SUPPLY_STATUS_UNKNOWN;
+		break;
+	case POWER_SUPPLY_PROP_TEMP:
+		ret = regmap_read(chip->regmap, REG_TEMPERATURE, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = DECIKELVIN_TO_DECIDEGC(regval);
+		break;
+	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG:
+		ret = regmap_read(chip->regmap, REG_AVERAGE_TIME_TO_EMPTY, &regval);
+		if (ret < 0)
+			return ret;
+
+		/* The estimation is not yet ready */
+		if (regval == U16_MAX)
+			return -ENODATA;
+
+		val->intval = regval;
+		break;
+	case POWER_SUPPLY_PROP_TIME_TO_FULL_AVG:
+		ret = regmap_read(chip->regmap, REG_AVERAGE_TIME_TO_FULL, &regval);
+		if (ret < 0)
+			return ret;
+
+		/* The estimation is not yet ready */
+		if (regval == U16_MAX)
+			return -ENODATA;
+
+		val->intval = regval;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		ret = regmap_read(chip->regmap, REG_VOLTAGE, &regval);
+		if (ret < 0)
+			return ret;
+
+		val->intval = 1000 * regval;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct power_supply_desc mm8013_desc = {
+	.name			= "mm8013",
+	.type			= POWER_SUPPLY_TYPE_BATTERY,
+	.properties		= mm8013_battery_props,
+	.num_properties		= ARRAY_SIZE(mm8013_battery_props),
+	.get_property		= mm8013_get_property,
+};
+
+static const struct regmap_config mm8013_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0x68,
+	.use_single_read = true,
+	.use_single_write = true,
+	.val_format_endian = REGMAP_ENDIAN_LITTLE,
+};
+
+static int mm8013_probe(struct i2c_client *client)
+{
+	struct power_supply_config psy_cfg = {};
+	struct device *dev = &client->dev;
+	struct power_supply *psy;
+	struct mm8013_chip *chip;
+	int ret = 0;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		return dev_err_probe(dev, -EIO,
+				     "I2C_FUNC_SMBUS_WORD_DATA not supported\n");
+
+	chip = devm_kzalloc(dev, sizeof(struct mm8013_chip), GFP_KERNEL);
+	if (!chip)
+		return -ENOMEM;
+
+	chip->client = client;
+
+	chip->regmap = devm_regmap_init_i2c(client, &mm8013_regmap_config);
+	if (IS_ERR(chip->regmap))
+		return dev_err_probe(dev, ret, "Couldn't initialize regmap\n");
+
+	ret = mm8013_checkdevice(chip);
+	if (ret)
+		return dev_err_probe(dev, ret, "MM8013 not found\n");
+
+	psy_cfg.drv_data = chip;
+	psy_cfg.of_node = dev->of_node;
+
+	psy = devm_power_supply_register(dev, &mm8013_desc, &psy_cfg);
+	if (IS_ERR(psy))
+		return PTR_ERR(psy);
+
+	return 0;
+}
+
+static const struct i2c_device_id mm8013_id_table[] = {
+	{ "mm8013", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, mm8013_id_table);
+
+static const struct of_device_id mm8013_match_table[] = {
+	{ .compatible = "mitsumi,mm8013" },
+	{}
+};
+
+static struct i2c_driver mm8013_i2c_driver = {
+	.probe = mm8013_probe,
+	.id_table = mm8013_id_table,
+	.driver = {
+		.name = "mm8013",
+		.of_match_table = mm8013_match_table,
+	},
+};
+module_i2c_driver(mm8013_i2c_driver);
+
+MODULE_DESCRIPTION("MM8013 fuel gauge driver");
+MODULE_LICENSE("GPL");