--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Helper for batteries with accurate current and voltage measurement, but
+ * without temperature measurement or without a "resistance-temp-table".
+ *
+ * Some fuel-gauges are not full-featured autonomous fuel-gauges.
+ * These fuel-gauges offer accurate current and voltage measurements but
+ * their coulomb-counters are intended to work together with an always on
+ * micro-controller monitoring the fuel-gauge.
+ *
+ * This adc-battery-helper code offers open-circuit-voltage (ocv) and through
+ * that capacity estimation for devices where such limited functionality
+ * fuel-gauges are exposed directly to Linux.
+ *
+ * This helper requires the hw to provide accurate battery current_now and
+ * voltage_now measurement and this helper the provides the following properties
+ * based on top of those readings:
+ *
+ * POWER_SUPPLY_PROP_STATUS
+ * POWER_SUPPLY_PROP_VOLTAGE_OCV
+ * POWER_SUPPLY_PROP_VOLTAGE_NOW
+ * POWER_SUPPLY_PROP_CURRENT_NOW
+ * POWER_SUPPLY_PROP_CAPACITY
+ *
+ * As well as optional the following properties assuming an always present
+ * system-scope battery, allowing direct use of adc_battery_helper_get_prop()
+ * in this common case:
+ * POWER_SUPPLY_PROP_PRESENT
+ * POWER_SUPPLY_PROP_SCOPE
+ *
+ * Using this helper is as simple as:
+ *
+ * 1. Embed a struct adc_battery_helper this MUST be the first member of
+ * the battery driver's data struct.
+ * 2. Use adc_battery_helper_props[] or add the above properties to
+ * the list of properties in power_supply_desc
+ * 3. Call adc_battery_helper_init() after registering the power_supply and
+ * before returning from the probe() function
+ * 4. Use adc_battery_helper_get_prop() as the power-supply's get_property()
+ * method, or call it for the above properties.
+ * 5. Use adc_battery_helper_external_power_changed() as the power-supply's
+ * external_power_changed() method or call it from that method.
+ * 6. Use adc_battery_helper_[suspend|resume]() as suspend-resume methods or
+ * call them from the driver's suspend-resume methods.
+ *
+ * The provided get_voltage_and_current_now() method will be called by this
+ * helper at adc_battery_helper_init() time and later.
+ *
+ * Copyright (c) 2021-2025 Hans de Goede <hansg@kernel.org>
+ */
+
+#include <linux/cleanup.h>
+#include <linux/devm-helpers.h>
+#include <linux/mutex.h>
+#include <linux/power_supply.h>
+#include <linux/workqueue.h>
+
+#include "adc-battery-helper.h"
+
+#define MOV_AVG_WINDOW_SIZE ADC_BAT_HELPER_MOV_AVG_WINDOW_SIZE
+#define INIT_POLL_TIME (5 * HZ)
+#define POLL_TIME (30 * HZ)
+#define SETTLE_TIME (1 * HZ)
+
+#define INIT_POLL_COUNT 30
+
+#define CURR_HYST_UA 65000
+
+#define LOW_BAT_UV 3700000
+#define FULL_BAT_HYST_UV 38000
+
+#define AMBIENT_TEMP_CELSIUS 25
+
+static int adc_battery_helper_get_status(struct adc_battery_helper *help)
+{
+ int full_uv =
+ help->psy->battery_info->constant_charge_voltage_max_uv - FULL_BAT_HYST_UV;
+
+ if (help->curr_ua > CURR_HYST_UA)
+ return POWER_SUPPLY_STATUS_CHARGING;
+
+ if (help->curr_ua < -CURR_HYST_UA)
+ return POWER_SUPPLY_STATUS_DISCHARGING;
+
+ if (help->supplied && help->ocv_avg_uv > full_uv)
+ return POWER_SUPPLY_STATUS_FULL;
+
+ return POWER_SUPPLY_STATUS_NOT_CHARGING;
+}
+
+static void adc_battery_helper_work(struct work_struct *work)
+{
+ struct adc_battery_helper *help = container_of(work, struct adc_battery_helper,
+ work.work);
+ int i, curr_diff_ua, volt_diff_uv, res_mohm, ret, win_size;
+ struct device *dev = help->psy->dev.parent;
+ int volt_uv, prev_volt_uv = help->volt_uv;
+ int curr_ua, prev_curr_ua = help->curr_ua;
+ bool prev_supplied = help->supplied;
+ int prev_status = help->status;
+
+ guard(mutex)(&help->lock);
+
+ ret = help->get_voltage_and_current_now(help->psy, &volt_uv, &curr_ua);
+ if (ret)
+ goto out;
+
+ help->volt_uv = volt_uv;
+ help->curr_ua = curr_ua;
+
+ help->ocv_uv[help->ocv_avg_index] =
+ help->volt_uv - help->curr_ua * help->intern_res_avg_mohm / 1000;
+ dev_dbg(dev, "volt-now: %d, curr-now: %d, volt-ocv: %d\n",
+ help->volt_uv, help->curr_ua, help->ocv_uv[help->ocv_avg_index]);
+ help->ocv_avg_index = (help->ocv_avg_index + 1) % MOV_AVG_WINDOW_SIZE;
+ help->poll_count++;
+
+ help->ocv_avg_uv = 0;
+ win_size = min(help->poll_count, MOV_AVG_WINDOW_SIZE);
+ for (i = 0; i < win_size; i++)
+ help->ocv_avg_uv += help->ocv_uv[i];
+ help->ocv_avg_uv /= win_size;
+
+ help->supplied = power_supply_am_i_supplied(help->psy);
+ help->status = adc_battery_helper_get_status(help);
+ if (help->status == POWER_SUPPLY_STATUS_FULL)
+ help->capacity = 100;
+ else
+ help->capacity = power_supply_batinfo_ocv2cap(help->psy->battery_info,
+ help->ocv_avg_uv,
+ AMBIENT_TEMP_CELSIUS);
+
+ /*
+ * Skip internal resistance calc on charger [un]plug and
+ * when the battery is almost empty (voltage low).
+ */
+ if (help->supplied != prev_supplied ||
+ help->volt_uv < LOW_BAT_UV ||
+ help->poll_count < 2)
+ goto out;
+
+ /*
+ * Assuming that the OCV voltage does not change significantly
+ * between 2 polls, then we can calculate the internal resistance
+ * on a significant current change by attributing all voltage
+ * change between the 2 readings to the internal resistance.
+ */
+ curr_diff_ua = abs(help->curr_ua - prev_curr_ua);
+ if (curr_diff_ua < CURR_HYST_UA)
+ goto out;
+
+ volt_diff_uv = abs(help->volt_uv - prev_volt_uv);
+ res_mohm = volt_diff_uv * 1000 / curr_diff_ua;
+
+ if ((res_mohm < (help->intern_res_avg_mohm * 2 / 3)) ||
+ (res_mohm > (help->intern_res_avg_mohm * 4 / 3))) {
+ dev_dbg(dev, "Ignoring outlier internal resistance %d mOhm\n", res_mohm);
+ goto out;
+ }
+
+ dev_dbg(dev, "Internal resistance %d mOhm\n", res_mohm);
+
+ help->intern_res_mohm[help->intern_res_avg_index] = res_mohm;
+ help->intern_res_avg_index = (help->intern_res_avg_index + 1) % MOV_AVG_WINDOW_SIZE;
+ help->intern_res_poll_count++;
+
+ help->intern_res_avg_mohm = 0;
+ win_size = min(help->intern_res_poll_count, MOV_AVG_WINDOW_SIZE);
+ for (i = 0; i < win_size; i++)
+ help->intern_res_avg_mohm += help->intern_res_mohm[i];
+ help->intern_res_avg_mohm /= win_size;
+
+out:
+ queue_delayed_work(system_wq, &help->work,
+ (help->poll_count <= INIT_POLL_COUNT) ?
+ INIT_POLL_TIME : POLL_TIME);
+
+ if (help->status != prev_status)
+ power_supply_changed(help->psy);
+}
+
+const enum power_supply_property adc_battery_helper_properties[] = {
+ POWER_SUPPLY_PROP_STATUS,
+ POWER_SUPPLY_PROP_VOLTAGE_NOW,
+ POWER_SUPPLY_PROP_VOLTAGE_OCV,
+ POWER_SUPPLY_PROP_CURRENT_NOW,
+ POWER_SUPPLY_PROP_CAPACITY,
+ POWER_SUPPLY_PROP_PRESENT,
+ POWER_SUPPLY_PROP_SCOPE,
+};
+EXPORT_SYMBOL_GPL(adc_battery_helper_properties);
+
+static_assert(ARRAY_SIZE(adc_battery_helper_properties) ==
+ ADC_HELPER_NUM_PROPERTIES);
+
+int adc_battery_helper_get_property(struct power_supply *psy,
+ enum power_supply_property psp,
+ union power_supply_propval *val)
+{
+ struct adc_battery_helper *help = power_supply_get_drvdata(psy);
+ int dummy, ret = 0;
+
+ /*
+ * Avoid racing with adc_battery_helper_work() while it is updating
+ * variables and avoid calling get_voltage_and_current_now() reentrantly.
+ */
+ guard(mutex)(&help->lock);
+
+ switch (psp) {
+ case POWER_SUPPLY_PROP_STATUS:
+ val->intval = help->status;
+ break;
+ case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+ ret = help->get_voltage_and_current_now(psy, &val->intval, &dummy);
+ break;
+ case POWER_SUPPLY_PROP_VOLTAGE_OCV:
+ val->intval = help->ocv_avg_uv;
+ break;
+ case POWER_SUPPLY_PROP_CURRENT_NOW:
+ ret = help->get_voltage_and_current_now(psy, &dummy, &val->intval);
+ break;
+ case POWER_SUPPLY_PROP_CAPACITY:
+ val->intval = help->capacity;
+ break;
+ case POWER_SUPPLY_PROP_PRESENT:
+ val->intval = 1;
+ break;
+ case POWER_SUPPLY_PROP_SCOPE:
+ val->intval = POWER_SUPPLY_SCOPE_SYSTEM;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(adc_battery_helper_get_property);
+
+void adc_battery_helper_external_power_changed(struct power_supply *psy)
+{
+ struct adc_battery_helper *help = power_supply_get_drvdata(psy);
+
+ dev_dbg(help->psy->dev.parent, "external power changed\n");
+ mod_delayed_work(system_wq, &help->work, SETTLE_TIME);
+}
+EXPORT_SYMBOL_GPL(adc_battery_helper_external_power_changed);
+
+static void adc_battery_helper_start_work(struct adc_battery_helper *help)
+{
+ help->poll_count = 0;
+ help->ocv_avg_index = 0;
+
+ queue_delayed_work(system_wq, &help->work, 0);
+ flush_delayed_work(&help->work);
+}
+
+int adc_battery_helper_init(struct adc_battery_helper *help, struct power_supply *psy,
+ adc_battery_helper_get_func get_voltage_and_current_now)
+{
+ struct device *dev = psy->dev.parent;
+ int ret;
+
+ help->psy = psy;
+ help->get_voltage_and_current_now = get_voltage_and_current_now;
+
+ ret = devm_mutex_init(dev, &help->lock);
+ if (ret)
+ return ret;
+
+ ret = devm_delayed_work_autocancel(dev, &help->work, adc_battery_helper_work);
+ if (ret)
+ return ret;
+
+ if (!help->psy->battery_info ||
+ help->psy->battery_info->factory_internal_resistance_uohm == -EINVAL ||
+ help->psy->battery_info->constant_charge_voltage_max_uv == -EINVAL ||
+ !psy->battery_info->ocv_table[0]) {
+ dev_err(dev, "error required properties are missing\n");
+ return -ENODEV;
+ }
+
+ /* Use provided internal resistance as start point (in milli-ohm) */
+ help->intern_res_avg_mohm =
+ help->psy->battery_info->factory_internal_resistance_uohm / 1000;
+ /* Also add it to the internal resistance moving average window */
+ help->intern_res_mohm[0] = help->intern_res_avg_mohm;
+ help->intern_res_avg_index = 1;
+ help->intern_res_poll_count = 1;
+
+ adc_battery_helper_start_work(help);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(adc_battery_helper_init);
+
+int adc_battery_helper_suspend(struct device *dev)
+{
+ struct adc_battery_helper *help = dev_get_drvdata(dev);
+
+ cancel_delayed_work_sync(&help->work);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(adc_battery_helper_suspend);
+
+int adc_battery_helper_resume(struct device *dev)
+{
+ struct adc_battery_helper *help = dev_get_drvdata(dev);
+
+ adc_battery_helper_start_work(help);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(adc_battery_helper_resume);
+
+MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
+MODULE_DESCRIPTION("ADC battery capacity estimation helper");
+MODULE_LICENSE("GPL");
--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Helper for batteries with accurate current and voltage measurement, but
+ * without temperature measurement or without a "resistance-temp-table".
+ * Copyright (c) 2021-2025 Hans de Goede <hansg@kernel.org>
+ */
+
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+
+#define ADC_BAT_HELPER_MOV_AVG_WINDOW_SIZE 8
+
+struct power_supply;
+
+/*
+ * The adc battery helper code needs voltage- and current-now to be sampled as
+ * close to each other (in sample-time) as possible. A single getter function is
+ * used to allow the battery driver to handle this in the best way possible.
+ */
+typedef int (*adc_battery_helper_get_func)(struct power_supply *psy, int *volt, int *curr);
+
+struct adc_battery_helper {
+ struct power_supply *psy;
+ struct delayed_work work;
+ struct mutex lock;
+ adc_battery_helper_get_func get_voltage_and_current_now;
+ int ocv_uv[ADC_BAT_HELPER_MOV_AVG_WINDOW_SIZE]; /* micro-volt */
+ int intern_res_mohm[ADC_BAT_HELPER_MOV_AVG_WINDOW_SIZE]; /* milli-ohm */
+ int poll_count;
+ int ocv_avg_index;
+ int ocv_avg_uv; /* micro-volt */
+ int intern_res_poll_count;
+ int intern_res_avg_index;
+ int intern_res_avg_mohm; /* milli-ohm */
+ int volt_uv; /* micro-volt */
+ int curr_ua; /* micro-ampere */
+ int capacity; /* percent */
+ int status;
+ bool supplied;
+};
+
+extern const enum power_supply_property adc_battery_helper_properties[];
+/* Must be const cannot be an external. Asserted in adc-battery-helper.c */
+#define ADC_HELPER_NUM_PROPERTIES 7
+
+int adc_battery_helper_init(struct adc_battery_helper *help, struct power_supply *psy,
+ adc_battery_helper_get_func get_voltage_and_current_now);
+/*
+ * The below functions can be directly used as power-supply / suspend-resume
+ * callbacks. They cast the power_supply_get_drvdata() / dev_get_drvdata() data
+ * directly to struct adc_battery_helper. Therefor struct adc_battery_helper
+ * MUST be the first member of the battery driver's data struct.
+ */
+int adc_battery_helper_get_property(struct power_supply *psy,
+ enum power_supply_property psp,
+ union power_supply_propval *val);
+void adc_battery_helper_external_power_changed(struct power_supply *psy);
+int adc_battery_helper_suspend(struct device *dev);
+int adc_battery_helper_resume(struct device *dev);
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