/*
* Battery driver for LEGO MINDSTORMS EV3
*
* Copyright (C) 2017 David Lechner <david@lechnology.com>
*
* 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.
* This program is distributed "as is" WITHOUT ANY WARRANTY of any
* kind, whether express or implied; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/iio/consumer.h>
#include <linux/iio/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/power_supply.h>
struct lego_ev3_battery {
struct iio_channel *iio_v;
struct iio_channel *iio_i;
struct gpio_desc *rechargeable_gpio;
struct power_supply *psy;
int technology;
int v_max;
int v_min;
};
static int lego_ev3_battery_get_property(struct power_supply *psy,
enum power_supply_property psp,
union power_supply_propval *val)
{
struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);
int ret, val2;
switch (psp) {
case POWER_SUPPLY_PROP_TECHNOLOGY:
val->intval = batt->technology;
break;
case POWER_SUPPLY_PROP_VOLTAGE_NOW:
/* battery voltage is iio channel * 2 + Vce of transistor */
ret = iio_read_channel_processed(batt->iio_v, &val->intval);
if (ret)
return ret;
val->intval *= 2000;
val->intval += 50000;
/* plus adjust for shunt resistor drop */
ret = iio_read_channel_processed(batt->iio_i, &val2);
if (ret)
return ret;
val2 *= 1000;
val2 /= 15;
val->intval += val2;
break;
case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
val->intval = batt->v_max;
break;
case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
val->intval = batt->v_min;
break;
case POWER_SUPPLY_PROP_CURRENT_NOW:
/* battery current is iio channel / 15 / 0.05 ohms */
ret = iio_read_channel_processed(batt->iio_i, &val->intval);
if (ret)
return ret;
val->intval *= 20000;
val->intval /= 15;
break;
case POWER_SUPPLY_PROP_SCOPE:
val->intval = POWER_SUPPLY_SCOPE_SYSTEM;
break;
default:
return -EINVAL;
}
return 0;
}
static int lego_ev3_battery_set_property(struct power_supply *psy,
enum power_supply_property psp,
const union power_supply_propval *val)
{
struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);
switch (psp) {
case POWER_SUPPLY_PROP_TECHNOLOGY:
/*
* Only allow changing technology from Unknown to NiMH. Li-ion
* batteries are automatically detected and should not be
* overridden. Rechargeable AA batteries, on the other hand,
* cannot be automatically detected, and so must be manually
* specified. This should only be set once during system init,
* so there is no mechanism to go back to Unknown.
*/
if (batt->technology != POWER_SUPPLY_TECHNOLOGY_UNKNOWN)
return -EINVAL;
switch (val->intval) {
case POWER_SUPPLY_TECHNOLOGY_NiMH:
batt->technology = POWER_SUPPLY_TECHNOLOGY_NiMH;
batt->v_max = 7800000;
batt->v_min = 5400000;
break;
default:
return -EINVAL;
}
break;
default:
return -EINVAL;
}
return 0;
}
static int lego_ev3_battery_property_is_writeable(struct power_supply *psy,
enum power_supply_property psp)
{
struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);
return psp == POWER_SUPPLY_PROP_TECHNOLOGY &&
batt->technology == POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
}
static enum power_supply_property lego_ev3_battery_props[] = {
POWER_SUPPLY_PROP_TECHNOLOGY,
POWER_SUPPLY_PROP_VOLTAGE_NOW,
POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
POWER_SUPPLY_PROP_CURRENT_NOW,
POWER_SUPPLY_PROP_SCOPE,
};
static const struct power_supply_desc lego_ev3_battery_desc = {
.name = "lego-ev3-battery",
.type = POWER_SUPPLY_TYPE_BATTERY,
.properties = lego_ev3_battery_props,
.num_properties = ARRAY_SIZE(lego_ev3_battery_props),
.get_property = lego_ev3_battery_get_property,
.set_property = lego_ev3_battery_set_property,
.property_is_writeable = lego_ev3_battery_property_is_writeable,
};
static int lego_ev3_battery_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct lego_ev3_battery *batt;
struct power_supply_config psy_cfg = {};
int err;
batt = devm_kzalloc(dev, sizeof(*batt), GFP_KERNEL);
if (!batt)
return -ENOMEM;
platform_set_drvdata(pdev, batt);
batt->iio_v = devm_iio_channel_get(dev, "voltage");
err = PTR_ERR_OR_ZERO(batt->iio_v);
if (err)
return dev_err_probe(dev, err,
"Failed to get voltage iio channel\n");
batt->iio_i = devm_iio_channel_get(dev, "current");
err = PTR_ERR_OR_ZERO(batt->iio_i);
if (err)
return dev_err_probe(dev, err,
"Failed to get current iio channel\n");
batt->rechargeable_gpio = devm_gpiod_get(dev, "rechargeable", GPIOD_IN);
err = PTR_ERR_OR_ZERO(batt->rechargeable_gpio);
if (err)
return dev_err_probe(dev, err,
"Failed to get rechargeable gpio\n");
/*
* The rechargeable battery indication switch cannot be changed without
* removing the battery, so we only need to read it once.
*/
if (gpiod_get_value(batt->rechargeable_gpio)) {
/* 2-cell Li-ion, 7.4V nominal */
batt->technology = POWER_SUPPLY_TECHNOLOGY_LION;
batt->v_max = 84000000;
batt->v_min = 60000000;
} else {
/* 6x AA Alkaline, 9V nominal */
batt->technology = POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
batt->v_max = 90000000;
batt->v_min = 48000000;
}
psy_cfg.of_node = pdev->dev.of_node;
psy_cfg.drv_data = batt;
batt->psy = devm_power_supply_register(dev, &lego_ev3_battery_desc,
&psy_cfg);
err = PTR_ERR_OR_ZERO(batt->psy);
if (err) {
dev_err(dev, "failed to register power supply\n");
return err;
}
return 0;
}
static const struct of_device_id of_lego_ev3_battery_match[] = {
{ .compatible = "lego,ev3-battery", },
{ }
};
MODULE_DEVICE_TABLE(of, of_lego_ev3_battery_match);
static struct platform_driver lego_ev3_battery_driver = {
.driver = {
.name = "lego-ev3-battery",
.of_match_table = of_lego_ev3_battery_match,
},
.probe = lego_ev3_battery_probe,
};
module_platform_driver(lego_ev3_battery_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Lechner <david@lechnology.com>");
MODULE_DESCRIPTION("LEGO MINDSTORMS EV3 Battery Driver");