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1/*2 * Battery driver for LEGO MINDSTORMS EV33 *4 * Copyright (C) 2017 David Lechner <david@lechnology.com>5 *6 * This program is free software; you can redistribute it and/or modify7 * it under the terms of the GNU General Public License version 2 as8 * published by the Free Software Foundation.9 10 * This program is distributed "as is" WITHOUT ANY WARRANTY of any11 * kind, whether express or implied; without even the implied warranty12 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the13 * GNU General Public License for more details.14 */15 16#include <linux/delay.h>17#include <linux/err.h>18#include <linux/gpio/consumer.h>19#include <linux/iio/consumer.h>20#include <linux/iio/types.h>21#include <linux/kernel.h>22#include <linux/module.h>23#include <linux/mod_devicetable.h>24#include <linux/platform_device.h>25#include <linux/power_supply.h>26 27struct lego_ev3_battery {28 struct iio_channel *iio_v;29 struct iio_channel *iio_i;30 struct gpio_desc *rechargeable_gpio;31 struct power_supply *psy;32 int technology;33 int v_max;34 int v_min;35};36 37static int lego_ev3_battery_get_property(struct power_supply *psy,38 enum power_supply_property psp,39 union power_supply_propval *val)40{41 struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);42 int ret, val2;43 44 switch (psp) {45 case POWER_SUPPLY_PROP_TECHNOLOGY:46 val->intval = batt->technology;47 break;48 case POWER_SUPPLY_PROP_VOLTAGE_NOW:49 /* battery voltage is iio channel * 2 + Vce of transistor */50 ret = iio_read_channel_processed(batt->iio_v, &val->intval);51 if (ret)52 return ret;53 54 val->intval *= 2000;55 val->intval += 50000;56 57 /* plus adjust for shunt resistor drop */58 ret = iio_read_channel_processed(batt->iio_i, &val2);59 if (ret)60 return ret;61 62 val2 *= 1000;63 val2 /= 15;64 val->intval += val2;65 break;66 case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:67 val->intval = batt->v_max;68 break;69 case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:70 val->intval = batt->v_min;71 break;72 case POWER_SUPPLY_PROP_CURRENT_NOW:73 /* battery current is iio channel / 15 / 0.05 ohms */74 ret = iio_read_channel_processed(batt->iio_i, &val->intval);75 if (ret)76 return ret;77 78 val->intval *= 20000;79 val->intval /= 15;80 break;81 case POWER_SUPPLY_PROP_SCOPE:82 val->intval = POWER_SUPPLY_SCOPE_SYSTEM;83 break;84 default:85 return -EINVAL;86 }87 88 return 0;89}90 91static int lego_ev3_battery_set_property(struct power_supply *psy,92 enum power_supply_property psp,93 const union power_supply_propval *val)94{95 struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);96 97 switch (psp) {98 case POWER_SUPPLY_PROP_TECHNOLOGY:99 /*100 * Only allow changing technology from Unknown to NiMH. Li-ion101 * batteries are automatically detected and should not be102 * overridden. Rechargeable AA batteries, on the other hand,103 * cannot be automatically detected, and so must be manually104 * specified. This should only be set once during system init,105 * so there is no mechanism to go back to Unknown.106 */107 if (batt->technology != POWER_SUPPLY_TECHNOLOGY_UNKNOWN)108 return -EINVAL;109 switch (val->intval) {110 case POWER_SUPPLY_TECHNOLOGY_NiMH:111 batt->technology = POWER_SUPPLY_TECHNOLOGY_NiMH;112 batt->v_max = 7800000;113 batt->v_min = 5400000;114 break;115 default:116 return -EINVAL;117 }118 break;119 default:120 return -EINVAL;121 }122 123 return 0;124}125 126static int lego_ev3_battery_property_is_writeable(struct power_supply *psy,127 enum power_supply_property psp)128{129 struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);130 131 return psp == POWER_SUPPLY_PROP_TECHNOLOGY &&132 batt->technology == POWER_SUPPLY_TECHNOLOGY_UNKNOWN;133}134 135static enum power_supply_property lego_ev3_battery_props[] = {136 POWER_SUPPLY_PROP_TECHNOLOGY,137 POWER_SUPPLY_PROP_VOLTAGE_NOW,138 POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,139 POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,140 POWER_SUPPLY_PROP_CURRENT_NOW,141 POWER_SUPPLY_PROP_SCOPE,142};143 144static const struct power_supply_desc lego_ev3_battery_desc = {145 .name = "lego-ev3-battery",146 .type = POWER_SUPPLY_TYPE_BATTERY,147 .properties = lego_ev3_battery_props,148 .num_properties = ARRAY_SIZE(lego_ev3_battery_props),149 .get_property = lego_ev3_battery_get_property,150 .set_property = lego_ev3_battery_set_property,151 .property_is_writeable = lego_ev3_battery_property_is_writeable,152};153 154static int lego_ev3_battery_probe(struct platform_device *pdev)155{156 struct device *dev = &pdev->dev;157 struct lego_ev3_battery *batt;158 struct power_supply_config psy_cfg = {};159 int err;160 161 batt = devm_kzalloc(dev, sizeof(*batt), GFP_KERNEL);162 if (!batt)163 return -ENOMEM;164 165 platform_set_drvdata(pdev, batt);166 167 batt->iio_v = devm_iio_channel_get(dev, "voltage");168 err = PTR_ERR_OR_ZERO(batt->iio_v);169 if (err)170 return dev_err_probe(dev, err,171 "Failed to get voltage iio channel\n");172 173 batt->iio_i = devm_iio_channel_get(dev, "current");174 err = PTR_ERR_OR_ZERO(batt->iio_i);175 if (err)176 return dev_err_probe(dev, err,177 "Failed to get current iio channel\n");178 179 batt->rechargeable_gpio = devm_gpiod_get(dev, "rechargeable", GPIOD_IN);180 err = PTR_ERR_OR_ZERO(batt->rechargeable_gpio);181 if (err)182 return dev_err_probe(dev, err,183 "Failed to get rechargeable gpio\n");184 185 /*186 * The rechargeable battery indication switch cannot be changed without187 * removing the battery, so we only need to read it once.188 */189 if (gpiod_get_value(batt->rechargeable_gpio)) {190 /* 2-cell Li-ion, 7.4V nominal */191 batt->technology = POWER_SUPPLY_TECHNOLOGY_LION;192 batt->v_max = 84000000;193 batt->v_min = 60000000;194 } else {195 /* 6x AA Alkaline, 9V nominal */196 batt->technology = POWER_SUPPLY_TECHNOLOGY_UNKNOWN;197 batt->v_max = 90000000;198 batt->v_min = 48000000;199 }200 201 psy_cfg.of_node = pdev->dev.of_node;202 psy_cfg.drv_data = batt;203 204 batt->psy = devm_power_supply_register(dev, &lego_ev3_battery_desc,205 &psy_cfg);206 err = PTR_ERR_OR_ZERO(batt->psy);207 if (err) {208 dev_err(dev, "failed to register power supply\n");209 return err;210 }211 212 return 0;213}214 215static const struct of_device_id of_lego_ev3_battery_match[] = {216 { .compatible = "lego,ev3-battery", },217 { }218};219MODULE_DEVICE_TABLE(of, of_lego_ev3_battery_match);220 221static struct platform_driver lego_ev3_battery_driver = {222 .driver = {223 .name = "lego-ev3-battery",224 .of_match_table = of_lego_ev3_battery_match,225 },226 .probe = lego_ev3_battery_probe,227};228module_platform_driver(lego_ev3_battery_driver);229 230MODULE_LICENSE("GPL");231MODULE_AUTHOR("David Lechner <david@lechnology.com>");232MODULE_DESCRIPTION("LEGO MINDSTORMS EV3 Battery Driver");233