/*
 * Driver for SBS compliant Smart Battery System Managers
 *
 * The device communicates via i2c at address 0x0a and multiplexes access to up
 * to four smart batteries at address 0x0b.
 *
 * Via sysfs interface the online state and charge type are presented.
 *
 * Datasheet SBSM:    http://sbs-forum.org/specs/sbsm100b.pdf
 * Datasheet LTC1760: http://cds.linear.com/docs/en/datasheet/1760fb.pdf
 *
 * Karl-Heinz Schneider <karl-heinz@schneider-inet.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/power_supply.h>
#include <linux/property.h>

#define SBSM_MAX_BATS  4
#define SBSM_RETRY_CNT 3

/* registers addresses */
#define SBSM_CMD_BATSYSSTATE     0x01
#define SBSM_CMD_BATSYSSTATECONT 0x02
#define SBSM_CMD_BATSYSINFO      0x04
#define SBSM_CMD_LTC             0x3c

#define SBSM_MASK_BAT_SUPPORTED  GENMASK(3, 0)
#define SBSM_MASK_CHARGE_BAT     GENMASK(7, 4)
#define SBSM_BIT_AC_PRESENT      BIT(0)
#define SBSM_BIT_TURBO           BIT(7)

#define SBSM_SMB_BAT_OFFSET      11
struct sbsm_data {
	struct i2c_client *client;
	struct i2c_mux_core *muxc;

	struct power_supply *psy;

	u8 cur_chan;          /* currently selected channel */
	struct gpio_chip chip;
	bool is_ltc1760;      /* special capabilities */

	unsigned int supported_bats;
	unsigned int last_state;
	unsigned int last_state_cont;
};

static enum power_supply_property sbsm_props[] = {
	POWER_SUPPLY_PROP_ONLINE,
	POWER_SUPPLY_PROP_CHARGE_TYPE,
};

static int sbsm_read_word(struct i2c_client *client, u8 address)
{
	int reg, retries;

	for (retries = SBSM_RETRY_CNT; retries > 0; retries--) {
		reg = i2c_smbus_read_word_data(client, address);
		if (reg >= 0)
			break;
	}

	if (reg < 0) {
		dev_err(&client->dev, "failed to read register 0x%02x\n",
			address);
	}

	return reg;
}

static int sbsm_write_word(struct i2c_client *client, u8 address, u16 word)
{
	int ret, retries;

	for (retries = SBSM_RETRY_CNT; retries > 0; retries--) {
		ret = i2c_smbus_write_word_data(client, address, word);
		if (ret >= 0)
			break;
	}
	if (ret < 0)
		dev_err(&client->dev, "failed to write to register 0x%02x\n",
			address);

	return ret;
}

static int sbsm_get_property(struct power_supply *psy,
			     enum power_supply_property psp,
			     union power_supply_propval *val)
{
	struct sbsm_data *data = power_supply_get_drvdata(psy);
	int regval = 0;

	switch (psp) {
	case POWER_SUPPLY_PROP_ONLINE:
		regval = sbsm_read_word(data->client, SBSM_CMD_BATSYSSTATECONT);
		if (regval < 0)
			return regval;
		val->intval = !!(regval & SBSM_BIT_AC_PRESENT);
		break;

	case POWER_SUPPLY_PROP_CHARGE_TYPE:
		regval = sbsm_read_word(data->client, SBSM_CMD_BATSYSSTATE);
		if (regval < 0)
			return regval;

		if ((regval & SBSM_MASK_CHARGE_BAT) == 0) {
			val->intval = POWER_SUPPLY_CHARGE_TYPE_NONE;
			return 0;
		}
		val->intval = POWER_SUPPLY_CHARGE_TYPE_TRICKLE;

		if (data->is_ltc1760) {
			/* charge mode fast if turbo is active */
			regval = sbsm_read_word(data->client, SBSM_CMD_LTC);
			if (regval < 0)
				return regval;
			else if (regval & SBSM_BIT_TURBO)
				val->intval = POWER_SUPPLY_CHARGE_TYPE_FAST;
		}
		break;

	default:
		return -EINVAL;
	}

	return 0;
}

static int sbsm_prop_is_writeable(struct power_supply *psy,
				  enum power_supply_property psp)
{
	struct sbsm_data *data = power_supply_get_drvdata(psy);

	return (psp == POWER_SUPPLY_PROP_CHARGE_TYPE) && data->is_ltc1760;
}

static int sbsm_set_property(struct power_supply *psy,
			     enum power_supply_property psp,
			     const union power_supply_propval *val)
{
	struct sbsm_data *data = power_supply_get_drvdata(psy);
	int ret = -EINVAL;
	u16 regval;

	switch (psp) {
	case POWER_SUPPLY_PROP_CHARGE_TYPE:
		/* write 1 to TURBO if type fast is given */
		if (!data->is_ltc1760)
			break;
		regval = val->intval ==
			 POWER_SUPPLY_CHARGE_TYPE_FAST ? SBSM_BIT_TURBO : 0;
		ret = sbsm_write_word(data->client, SBSM_CMD_LTC, regval);
		break;

	default:
		break;
	}

	return ret;
}

/*
 * Switch to battery
 * Parameter chan is directly the content of SMB_BAT* nibble
 */
static int sbsm_select(struct i2c_mux_core *muxc, u32 chan)
{
	struct sbsm_data *data = i2c_mux_priv(muxc);
	struct device *dev = &data->client->dev;
	int ret = 0;
	u16 reg;

	if (data->cur_chan == chan)
		return ret;

	/* chan goes from 1 ... 4 */
	reg = BIT(SBSM_SMB_BAT_OFFSET + chan);
	ret = sbsm_write_word(data->client, SBSM_CMD_BATSYSSTATE, reg);
	if (ret)
		dev_err(dev, "Failed to select channel %i\n", chan);
	else
		data->cur_chan = chan;

	return ret;
}

static int sbsm_gpio_get_value(struct gpio_chip *gc, unsigned int off)
{
	struct sbsm_data *data = gpiochip_get_data(gc);
	int ret;

	ret = sbsm_read_word(data->client, SBSM_CMD_BATSYSSTATE);
	if (ret < 0)
		return ret;

	return ret & BIT(off);
}

/*
 * This needs to be defined or the GPIO lib fails to register the pin.
 * But the 'gpio' is always an input.
 */
static int sbsm_gpio_direction_input(struct gpio_chip *gc, unsigned int off)
{
	return 0;
}

static int sbsm_do_alert(struct device *dev, void *d)
{
	struct i2c_client *client = i2c_verify_client(dev);
	struct i2c_driver *driver;

	if (!client || client->addr != 0x0b)
		return 0;

	device_lock(dev);
	if (client->dev.driver) {
		driver = to_i2c_driver(client->dev.driver);
		if (driver->alert)
			driver->alert(client, I2C_PROTOCOL_SMBUS_ALERT, 0);
		else
			dev_warn(&client->dev, "no driver alert()!\n");
	} else {
		dev_dbg(&client->dev, "alert with no driver\n");
	}
	device_unlock(dev);

	return -EBUSY;
}

static void sbsm_alert(struct i2c_client *client, enum i2c_alert_protocol prot,
		       unsigned int d)
{
	struct sbsm_data *sbsm = i2c_get_clientdata(client);

	int ret, i, irq_bat = 0, state = 0;

	ret = sbsm_read_word(sbsm->client, SBSM_CMD_BATSYSSTATE);
	if (ret >= 0) {
		irq_bat = ret ^ sbsm->last_state;
		sbsm->last_state = ret;
		state = ret;
	}

	ret = sbsm_read_word(sbsm->client, SBSM_CMD_BATSYSSTATECONT);
	if ((ret >= 0) &&
	    ((ret ^ sbsm->last_state_cont) & SBSM_BIT_AC_PRESENT)) {
		irq_bat |= sbsm->supported_bats & state;
		power_supply_changed(sbsm->psy);
	}
	sbsm->last_state_cont = ret;

	for (i = 0; i < SBSM_MAX_BATS; i++) {
		if (irq_bat & BIT(i)) {
			device_for_each_child(&sbsm->muxc->adapter[i]->dev,
					      NULL, sbsm_do_alert);
		}
	}
}

static int sbsm_gpio_setup(struct sbsm_data *data)
{
	struct gpio_chip *gc = &data->chip;
	struct i2c_client *client = data->client;
	struct device *dev = &client->dev;
	int ret;

	if (!device_property_present(dev, "gpio-controller"))
		return 0;

	ret  = sbsm_read_word(client, SBSM_CMD_BATSYSSTATE);
	if (ret < 0)
		return ret;
	data->last_state = ret;

	ret  = sbsm_read_word(client, SBSM_CMD_BATSYSSTATECONT);
	if (ret < 0)
		return ret;
	data->last_state_cont = ret;

	gc->get = sbsm_gpio_get_value;
	gc->direction_input  = sbsm_gpio_direction_input;
	gc->can_sleep = true;
	gc->base = -1;
	gc->ngpio = SBSM_MAX_BATS;
	gc->label = client->name;
	gc->parent = dev;
	gc->owner = THIS_MODULE;

	ret = devm_gpiochip_add_data(dev, gc, data);
	if (ret) {
		dev_err(dev, "devm_gpiochip_add_data failed: %d\n", ret);
		return ret;
	}

	return ret;
}

static const struct power_supply_desc sbsm_default_psy_desc = {
	.type = POWER_SUPPLY_TYPE_MAINS,
	.properties = sbsm_props,
	.num_properties = ARRAY_SIZE(sbsm_props),
	.get_property = &sbsm_get_property,
	.set_property = &sbsm_set_property,
	.property_is_writeable = &sbsm_prop_is_writeable,
};

static int sbsm_probe(struct i2c_client *client,
		      const struct i2c_device_id *id)
{
	struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
	struct sbsm_data *data;
	struct device *dev = &client->dev;
	struct power_supply_desc *psy_desc;
	struct power_supply_config psy_cfg = {};
	int ret = 0, i;

	/* Device listens only at address 0x0a */
	if (client->addr != 0x0a)
		return -EINVAL;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WORD_DATA))
		return -EPFNOSUPPORT;

	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	i2c_set_clientdata(client, data);

	data->client = client;
	data->is_ltc1760 = !!strstr(id->name, "ltc1760");

	ret  = sbsm_read_word(client, SBSM_CMD_BATSYSINFO);
	if (ret < 0)
		return ret;
	data->supported_bats = ret & SBSM_MASK_BAT_SUPPORTED;
	data->muxc = i2c_mux_alloc(adapter, dev, SBSM_MAX_BATS, 0,
				   I2C_MUX_LOCKED, &sbsm_select, NULL);
	if (!data->muxc) {
		dev_err(dev, "failed to alloc i2c mux\n");
		ret = -ENOMEM;
		goto err_mux_alloc;
	}
	data->muxc->priv = data;

	/* register muxed i2c channels. One for each supported battery */
	for (i = 0; i < SBSM_MAX_BATS; ++i) {
		if (data->supported_bats & BIT(i)) {
			ret = i2c_mux_add_adapter(data->muxc, 0, i + 1, 0);
			if (ret)
				break;
		}
	}
	if (ret) {
		dev_err(dev, "failed to register i2c mux channel %d\n", i + 1);
		goto err_mux_register;
	}

	psy_desc = devm_kmemdup(dev, &sbsm_default_psy_desc,
				sizeof(struct power_supply_desc),
				GFP_KERNEL);
	if (!psy_desc) {
		ret = -ENOMEM;
		goto err_psy;
	}

	psy_desc->name = devm_kasprintf(dev, GFP_KERNEL, "sbsm-%s",
					dev_name(&client->dev));
	if (!psy_desc->name) {
		ret = -ENOMEM;
		goto err_psy;
	}
	ret = sbsm_gpio_setup(data);
	if (ret < 0)
		goto err_psy;

	psy_cfg.drv_data = data;
	psy_cfg.of_node = dev->of_node;
	data->psy = devm_power_supply_register(dev, psy_desc, &psy_cfg);
	if (IS_ERR(data->psy)) {
		ret = PTR_ERR(data->psy);
		dev_err(dev, "failed to register power supply %s\n",
			psy_desc->name);
		goto err_psy;
	}

	return 0;

err_psy:
err_mux_register:
	i2c_mux_del_adapters(data->muxc);

err_mux_alloc:
	return ret;
}

static int sbsm_remove(struct i2c_client *client)
{
	struct sbsm_data *data = i2c_get_clientdata(client);

	i2c_mux_del_adapters(data->muxc);
	return 0;
}

static const struct i2c_device_id sbsm_ids[] = {
	{ "sbs-manager", 0 },
	{ "ltc1760",     0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, sbsm_ids);

#ifdef CONFIG_OF
static const struct of_device_id sbsm_dt_ids[] = {
	{ .compatible = "sbs,sbs-manager" },
	{ .compatible = "lltc,ltc1760" },
	{ }
};
MODULE_DEVICE_TABLE(of, sbsm_dt_ids);
#endif

static struct i2c_driver sbsm_driver = {
	.driver = {
		.name = "sbsm",
		.of_match_table = of_match_ptr(sbsm_dt_ids),
	},
	.probe		= sbsm_probe,
	.remove		= sbsm_remove,
	.alert		= sbsm_alert,
	.id_table	= sbsm_ids
};
module_i2c_driver(sbsm_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Karl-Heinz Schneider <karl-heinz@schneider-inet.de>");
MODULE_DESCRIPTION("SBSM Smart Battery System Manager");