ltc2941-battery-gauge.c

/*
 * I2C client/driver for the Linear Technology LTC2941 and LTC2943
 * Battery Gas Gauge IC
 *
 * Copyright (C) 2014 Topic Embedded Systems
 *
 * Author: Auryn Verwegen
 * Author: Mike Looijmans
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/swab.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/power_supply.h>
#include <linux/slab.h>

#define I16_MSB(x)			((x >> 8) & 0xFF)
#define I16_LSB(x)			(x & 0xFF)

#define LTC294X_WORK_DELAY		10	/* Update delay in seconds */

#define LTC294X_MAX_VALUE		0xFFFF
#define LTC294X_MID_SUPPLY		0x7FFF

#define LTC2941_MAX_PRESCALER_EXP	7
#define LTC2943_MAX_PRESCALER_EXP	6

enum ltc294x_reg {
	LTC294X_REG_STATUS		= 0x00,
	LTC294X_REG_CONTROL		= 0x01,
	LTC294X_REG_ACC_CHARGE_MSB	= 0x02,
	LTC294X_REG_ACC_CHARGE_LSB	= 0x03,
	LTC294X_REG_VOLTAGE_MSB		= 0x08,
	LTC294X_REG_VOLTAGE_LSB		= 0x09,
	LTC2942_REG_TEMPERATURE_MSB	= 0x0C,
	LTC2942_REG_TEMPERATURE_LSB	= 0x0D,
	LTC2943_REG_CURRENT_MSB		= 0x0E,
	LTC2943_REG_CURRENT_LSB		= 0x0F,
	LTC2943_REG_TEMPERATURE_MSB	= 0x14,
	LTC2943_REG_TEMPERATURE_LSB	= 0x15,
};

enum ltc294x_id {
	LTC2941_ID,
	LTC2943_ID,
};

#define LTC2943_REG_CONTROL_MODE_MASK (BIT(7) | BIT(6))
#define LTC2943_REG_CONTROL_MODE_SCAN BIT(7)
#define LTC294X_REG_CONTROL_PRESCALER_MASK	(BIT(5) | BIT(4) | BIT(3))
#define LTC294X_REG_CONTROL_SHUTDOWN_MASK	(BIT(0))
#define LTC294X_REG_CONTROL_PRESCALER_SET(x) \
	((x << 3) & LTC294X_REG_CONTROL_PRESCALER_MASK)
#define LTC294X_REG_CONTROL_ALCC_CONFIG_DISABLED	0

struct ltc294x_info {
	struct i2c_client *client;	/* I2C Client pointer */
	struct power_supply *supply;	/* Supply pointer */
	struct power_supply_desc supply_desc;	/* Supply description */
	struct delayed_work work;	/* Work scheduler */
	enum ltc294x_id id;		/* Chip type */
	int charge;	/* Last charge register content */
	int r_sense;	/* mOhm */
	int Qlsb;	/* nAh */
};

static inline int convert_bin_to_uAh(
	const struct ltc294x_info *info, int Q)
{
	return ((Q * (info->Qlsb / 10))) / 100;
}

static inline int convert_uAh_to_bin(
	const struct ltc294x_info *info, int uAh)
{
	int Q;

	Q = (uAh * 100) / (info->Qlsb/10);
	return (Q < LTC294X_MAX_VALUE) ? Q : LTC294X_MAX_VALUE;
}

static int ltc294x_read_regs(struct i2c_client *client,
	enum ltc294x_reg reg, u8 *buf, int num_regs)
{
	int ret;
	struct i2c_msg msgs[2] = { };
	u8 reg_start = reg;

	msgs[0].addr	= client->addr;
	msgs[0].len	= 1;
	msgs[0].buf	= &reg_start;

	msgs[1].addr	= client->addr;
	msgs[1].len	= num_regs;
	msgs[1].buf	= buf;
	msgs[1].flags	= I2C_M_RD;

	ret = i2c_transfer(client->adapter, &msgs[0], 2);
	if (ret < 0) {
		dev_err(&client->dev, "ltc2941 read_reg failed!\n");
		return ret;
	}

	dev_dbg(&client->dev, "%s (%#x, %d) -> %#x\n",
		__func__, reg, num_regs, *buf);

	return 0;
}

static int ltc294x_write_regs(struct i2c_client *client,
	enum ltc294x_reg reg, const u8 *buf, int num_regs)
{
	int ret;
	u8 reg_start = reg;

	ret = i2c_smbus_write_i2c_block_data(client, reg_start, num_regs, buf);
	if (ret < 0) {
		dev_err(&client->dev, "ltc2941 write_reg failed!\n");
		return ret;
	}

	dev_dbg(&client->dev, "%s (%#x, %d) -> %#x\n",
		__func__, reg, num_regs, *buf);

	return 0;
}

static int ltc294x_reset(const struct ltc294x_info *info, int prescaler_exp)
{
	int ret;
	u8 value;
	u8 control;

	/* Read status and control registers */
	ret = ltc294x_read_regs(info->client, LTC294X_REG_CONTROL, &value, 1);
	if (ret < 0) {
		dev_err(&info->client->dev,
			"Could not read registers from device\n");
		goto error_exit;
	}

	control = LTC294X_REG_CONTROL_PRESCALER_SET(prescaler_exp) |
				LTC294X_REG_CONTROL_ALCC_CONFIG_DISABLED;
	/* Put the 2943 into "monitor" mode, so it measures every 10 sec */
	if (info->id == LTC2941_ID)
		control |= LTC2943_REG_CONTROL_MODE_SCAN;

	if (value != control) {
		ret = ltc294x_write_regs(info->client,
			LTC294X_REG_CONTROL, &control, 1);
		if (ret < 0) {
			dev_err(&info->client->dev,
				"Could not write register\n");
			goto error_exit;
		}
	}

	return 0;

error_exit:
	return ret;
}

static int ltc294x_read_charge_register(const struct ltc294x_info *info)
{
	int ret;
	u8 datar[2];

	ret = ltc294x_read_regs(info->client,
		LTC294X_REG_ACC_CHARGE_MSB, &datar[0], 2);
	if (ret < 0)
		return ret;
	return (datar[0] << 8) + datar[1];
}

static int ltc294x_get_charge_now(const struct ltc294x_info *info, int *val)
{
	int value = ltc294x_read_charge_register(info);

	if (value < 0)
		return value;
	/* When r_sense < 0, this counts up when the battery discharges */
	if (info->Qlsb < 0)
		value -= 0xFFFF;
	*val = convert_bin_to_uAh(info, value);
	return 0;
}

static int ltc294x_set_charge_now(const struct ltc294x_info *info, int val)
{
	int ret;
	u8 dataw[2];
	u8 ctrl_reg;
	s32 value;

	value = convert_uAh_to_bin(info, val);
	/* Direction depends on how sense+/- were connected */
	if (info->Qlsb < 0)
		value += 0xFFFF;
	if ((value < 0) || (value > 0xFFFF)) /* input validation */
		return -EINVAL;

	/* Read control register */
	ret = ltc294x_read_regs(info->client,
		LTC294X_REG_CONTROL, &ctrl_reg, 1);
	if (ret < 0)
		return ret;
	/* Disable analog section */
	ctrl_reg |= LTC294X_REG_CONTROL_SHUTDOWN_MASK;
	ret = ltc294x_write_regs(info->client,
		LTC294X_REG_CONTROL, &ctrl_reg, 1);
	if (ret < 0)
		return ret;
	/* Set new charge value */
	dataw[0] = I16_MSB(value);
	dataw[1] = I16_LSB(value);
	ret = ltc294x_write_regs(info->client,
		LTC294X_REG_ACC_CHARGE_MSB, &dataw[0], 2);
	if (ret < 0)
		goto error_exit;
	/* Enable analog section */
error_exit:
	ctrl_reg &= ~LTC294X_REG_CONTROL_SHUTDOWN_MASK;
	ret = ltc294x_write_regs(info->client,
		LTC294X_REG_CONTROL, &ctrl_reg, 1);

	return ret < 0 ? ret : 0;
}

static int ltc294x_get_charge_counter(
	const struct ltc294x_info *info, int *val)
{
	int value = ltc294x_read_charge_register(info);

	if (value < 0)
		return value;
	value -= LTC294X_MID_SUPPLY;
	*val = convert_bin_to_uAh(info, value);
	return 0;
}

static int ltc294x_get_voltage(const struct ltc294x_info *info, int *val)
{
	int ret;
	u8 datar[2];
	u32 value;

	ret = ltc294x_read_regs(info->client,
		LTC294X_REG_VOLTAGE_MSB, &datar[0], 2);
	value = (datar[0] << 8) | datar[1];
	*val = ((value * 23600) / 0xFFFF) * 1000; /* in uV */
	return ret;
}

static int ltc294x_get_current(const struct ltc294x_info *info, int *val)
{
	int ret;
	u8 datar[2];
	s32 value;

	ret = ltc294x_read_regs(info->client,
		LTC2943_REG_CURRENT_MSB, &datar[0], 2);
	value = (datar[0] << 8) | datar[1];
	value -= 0x7FFF;
	/* Value is in range -32k..+32k, r_sense is usually 10..50 mOhm,
	 * the formula below keeps everything in s32 range while preserving
	 * enough digits */
	*val = 1000 * ((60000 * value) / (info->r_sense * 0x7FFF)); /* in uA */
	return ret;
}

static int ltc294x_get_temperature(const struct ltc294x_info *info, int *val)
{
	int ret;
	u8 datar[2];
	u32 value;

	ret = ltc294x_read_regs(info->client,
		LTC2943_REG_TEMPERATURE_MSB, &datar[0], 2);
	value = (datar[0] << 8) | datar[1];
	/* Full-scale is 510 Kelvin, convert to centidegrees  */
	*val = (((51000 * value) / 0xFFFF) - 27215);
	return ret;
}

static int ltc294x_get_property(struct power_supply *psy,
				enum power_supply_property prop,
				union power_supply_propval *val)
{
	struct ltc294x_info *info = power_supply_get_drvdata(psy);

	switch (prop) {
	case POWER_SUPPLY_PROP_CHARGE_NOW:
		return ltc294x_get_charge_now(info, &val->intval);
	case POWER_SUPPLY_PROP_CHARGE_COUNTER:
		return ltc294x_get_charge_counter(info, &val->intval);
	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
		return ltc294x_get_voltage(info, &val->intval);
	case POWER_SUPPLY_PROP_CURRENT_NOW:
		return ltc294x_get_current(info, &val->intval);
	case POWER_SUPPLY_PROP_TEMP:
		return ltc294x_get_temperature(info, &val->intval);
	default:
		return -EINVAL;
	}
}

static int ltc294x_set_property(struct power_supply *psy,
	enum power_supply_property psp,
	const union power_supply_propval *val)
{
	struct ltc294x_info *info = power_supply_get_drvdata(psy);

	switch (psp) {
	case POWER_SUPPLY_PROP_CHARGE_NOW:
		return ltc294x_set_charge_now(info, val->intval);
	default:
		return -EPERM;
	}
}

static int ltc294x_property_is_writeable(
	struct power_supply *psy, enum power_supply_property psp)
{
	switch (psp) {
	case POWER_SUPPLY_PROP_CHARGE_NOW:
		return 1;
	default:
		return 0;
	}
}

static void ltc294x_update(struct ltc294x_info *info)
{
	int charge = ltc294x_read_charge_register(info);

	if (charge != info->charge) {
		info->charge = charge;
		power_supply_changed(info->supply);
	}
}

static void ltc294x_work(struct work_struct *work)
{
	struct ltc294x_info *info;

	info = container_of(work, struct ltc294x_info, work.work);
	ltc294x_update(info);
	schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
}

static enum power_supply_property ltc294x_properties[] = {
	POWER_SUPPLY_PROP_CHARGE_COUNTER,
	POWER_SUPPLY_PROP_CHARGE_NOW,
	POWER_SUPPLY_PROP_VOLTAGE_NOW,
	POWER_SUPPLY_PROP_TEMP,
	POWER_SUPPLY_PROP_CURRENT_NOW,
};

static int ltc294x_i2c_remove(struct i2c_client *client)
{
	struct ltc294x_info *info = i2c_get_clientdata(client);

	cancel_delayed_work(&info->work);
	power_supply_unregister(info->supply);
	return 0;
}

static int ltc294x_i2c_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
{
	struct power_supply_config psy_cfg = {};
	struct ltc294x_info *info;
	int ret;
	u32 prescaler_exp;
	s32 r_sense;
	struct device_node *np;

	info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
	if (info == NULL)
		return -ENOMEM;

	i2c_set_clientdata(client, info);

	np = of_node_get(client->dev.of_node);

	info->id = (enum ltc294x_id)of_device_get_match_data(&client->dev);
	info->supply_desc.name = np->name;

	/* r_sense can be negative, when sense+ is connected to the battery
	 * instead of the sense-. This results in reversed measurements. */
	ret = of_property_read_u32(np, "lltc,resistor-sense", &r_sense);
	if (ret < 0) {
		dev_err(&client->dev,
			"Could not find lltc,resistor-sense in devicetree\n");
		return ret;
	}
	info->r_sense = r_sense;

	ret = of_property_read_u32(np, "lltc,prescaler-exponent",
		&prescaler_exp);
	if (ret < 0) {
		dev_warn(&client->dev,
			"lltc,prescaler-exponent not in devicetree\n");
		prescaler_exp = LTC2941_MAX_PRESCALER_EXP;
	}

	if (info->id == LTC2943_ID) {
		if (prescaler_exp > LTC2943_MAX_PRESCALER_EXP)
			prescaler_exp = LTC2943_MAX_PRESCALER_EXP;
		info->Qlsb = ((340 * 50000) / r_sense) /
				(4096 / (1 << (2*prescaler_exp)));
	} else {
		if (prescaler_exp > LTC2941_MAX_PRESCALER_EXP)
			prescaler_exp = LTC2941_MAX_PRESCALER_EXP;
		info->Qlsb = ((85 * 50000) / r_sense) /
				(128 / (1 << prescaler_exp));
	}

	info->client = client;
	info->supply_desc.type = POWER_SUPPLY_TYPE_BATTERY;
	info->supply_desc.properties = ltc294x_properties;
	switch (info->id) {
	case LTC2943_ID:
		info->supply_desc.num_properties =
			ARRAY_SIZE(ltc294x_properties);
		break;
	case LTC2941_ID:
	default:
		info->supply_desc.num_properties =
			ARRAY_SIZE(ltc294x_properties) - 3;
		break;
	}
	info->supply_desc.get_property = ltc294x_get_property;
	info->supply_desc.set_property = ltc294x_set_property;
	info->supply_desc.property_is_writeable = ltc294x_property_is_writeable;
	info->supply_desc.external_power_changed	= NULL;

	psy_cfg.drv_data = info;

	INIT_DELAYED_WORK(&info->work, ltc294x_work);

	ret = ltc294x_reset(info, prescaler_exp);
	if (ret < 0) {
		dev_err(&client->dev, "Communication with chip failed\n");
		return ret;
	}

	info->supply = power_supply_register(&client->dev, &info->supply_desc,
					     &psy_cfg);
	if (IS_ERR(info->supply)) {
		dev_err(&client->dev, "failed to register ltc2941\n");
		return PTR_ERR(info->supply);
	} else {
		schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
	}

	return 0;
}

#ifdef CONFIG_PM_SLEEP

static int ltc294x_suspend(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct ltc294x_info *info = i2c_get_clientdata(client);

	cancel_delayed_work(&info->work);
	return 0;
}

static int ltc294x_resume(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct ltc294x_info *info = i2c_get_clientdata(client);

	schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
	return 0;
}

static SIMPLE_DEV_PM_OPS(ltc294x_pm_ops, ltc294x_suspend, ltc294x_resume);
#define LTC294X_PM_OPS (&ltc294x_pm_ops)

#else
#define LTC294X_PM_OPS NULL
#endif /* CONFIG_PM_SLEEP */


static const struct i2c_device_id ltc294x_i2c_id[] = {
	{ "ltc2941", LTC2941_ID, },
	{ "ltc2943", LTC2943_ID, },
	{ },
};
MODULE_DEVICE_TABLE(i2c, ltc294x_i2c_id);

static const struct of_device_id ltc294x_i2c_of_match[] = {
	{
		.compatible = "lltc,ltc2941",
		.data = (void *)LTC2941_ID,
	},
	{
		.compatible = "lltc,ltc2943",
		.data = (void *)LTC2943_ID,
	},
	{ },
};
MODULE_DEVICE_TABLE(of, ltc294x_i2c_of_match);

static struct i2c_driver ltc294x_driver = {
	.driver = {
		.name	= "LTC2941",
		.of_match_table = ltc294x_i2c_of_match,
		.pm	= LTC294X_PM_OPS,
	},
	.probe		= ltc294x_i2c_probe,
	.remove		= ltc294x_i2c_remove,
	.id_table	= ltc294x_i2c_id,
};
module_i2c_driver(ltc294x_driver);

MODULE_AUTHOR("Auryn Verwegen, Topic Embedded Systems");
MODULE_AUTHOR("Mike Looijmans, Topic Embedded Products");
MODULE_DESCRIPTION("LTC2941/LTC2943 Battery Gas Gauge IC driver");
MODULE_LICENSE("GPL");