power: supply: ab8500: Standardize maintenance charging

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2071846
Tested: This is one of a series of patch sets to enable Arm SystemReady IR
 support in the kernel for NXP i.MX8 platforms.  This set updates the
 power subsystem.  This set has been tested via simple boot tests and
 the CI loop.

Conflicts:
    drivers/power/supply/ab8500-bm.h
    drivers/power/supply/ab8500_bmdata.c
    drivers/power/supply/abx500_chargalg.c

    This device is not currently support, so this part of the
    patch was ignored.

commit d72ce7d
Author: Linus Walleij <linus.walleij@linaro.org>
Date:   Sat Feb 26 00:27:55 2022 +0100

    power: supply: ab8500: Standardize maintenance charging

    Maintenance charging is the phase of keeping up the charge
    after the battery has charged fully using CC/CV charging.

    This can be done in many successive phases and is usually
    done with a slightly lower constant voltage than CV, and
    a slightly lower allowed current.

    Add an array of maintenance charging points each with a
    current, voltage and safety timer, and add helper functions
    to use these. Migrate the AB8500 code over.

    This is used in several Samsung products using the AB8500
    and these batteries and their complete parameters will
    be added later as full examples, but the default battery
    in the AB8500 code serves as a reasonable example so far.

    Reviewed-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
    Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
    (cherry picked from commit d72ce7d)

Signed-off-by: Al Stone <ahs3@redhat.com>

Author: Al Stone

drivers/power/supply/ab8500-bm.h

@@ -300,7 +300,6 @@ struct abx500_v_to_cap {
 	int voltage;
 	int capacity;
 };
-
 /* Forward declaration */
 struct abx500_fg;
 

drivers/power/supply/abx500_chargalg.c

@@ -888,7 +888,7 @@ static enum maxim_ret abx500_chargalg_chg_curr_maxim(struct abx500_chargalg *di)
 		di->ccm.max_current) {
 		if (di->ccm.condition_cnt-- == 0) {
 			/* Increse the iset with cco.test_delta_i */
-			di->ccm.condition_cnt = di->bm->maxi->wait_cycles;
+	di->ccm.condition_cnt = di->bm->maxi->wait_cycles;
 			di->ccm.current_iset += di->ccm.test_delta_i;
 			di->ccm.level++;
 			dev_dbg(di->dev, " Maximization needed, increase"
@@ -900,8 +900,8 @@ static enum maxim_ret abx500_chargalg_chg_curr_maxim(struct abx500_chargalg *di)
 				di->ccm.level);
 			return MAXIM_RET_CHANGE;
 		} else {
-			return MAXIM_RET_NOACTION;
-		}
+	return MAXIM_RET_NOACTION;
+}
 	}  else {
 		di->ccm.condition_cnt = di->bm->maxi->wait_cycles;
 		return MAXIM_RET_NOACTION;
@@ -1329,7 +1329,6 @@ static void abx500_chargalg_algorithm(struct abx500_chargalg *di)
 		di->charge_state == STATE_SUSPENDED) {
 		/* We don't do anything here, just don,t continue */
 	}
-
 	/* Safety timer expiration */
 	else if (di->events.safety_timer_expired) {
 		if (di->charge_state != STATE_SAFETY_TIMER_EXPIRED)
@@ -1443,7 +1442,6 @@ static void abx500_chargalg_algorithm(struct abx500_chargalg *di)
 	case STATE_SUSPENDED:
 		/* CHARGING is suspended */
 		break;
-
 	case STATE_BATT_REMOVED_INIT:
 		abx500_chargalg_stop_charging(di);
 		abx500_chargalg_state_to(di, STATE_BATT_REMOVED);
@@ -2060,7 +2058,6 @@ static int abx500_chargalg_probe(struct platform_device *pdev)
 		return ret;
 	}
 	di->curr_status.curr_step = CHARGALG_CURR_STEP_HIGH;
-
 	dev_info(di->dev, "probe success\n");
 	return component_add(dev, &abx500_chargalg_component_ops);
 }

drivers/power/supply/power_supply_core.c

@@ -595,6 +595,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
 	info->precharge_voltage_max_uv       = -EINVAL;
 	info->charge_restart_voltage_uv      = -EINVAL;
 	info->overvoltage_limit_uv           = -EINVAL;
+	info->maintenance_charge             = NULL;
 	info->temp_ambient_alert_min         = INT_MIN;
 	info->temp_ambient_alert_max         = INT_MAX;
 	info->temp_alert_min                 = INT_MIN;
@@ -844,6 +845,16 @@ int power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *t
 }
 EXPORT_SYMBOL_GPL(power_supply_temp2resist_simple);
 
+struct power_supply_maintenance_charge_table *
+power_supply_get_maintenance_charging_setting(struct power_supply_battery_info *info,
+					      int index)
+{
+	if (index >= info->maintenance_charge_size)
+		return NULL;
+	return &info->maintenance_charge[index];
+}
+EXPORT_SYMBOL_GPL(power_supply_get_maintenance_charging_setting);
+
 /**
  * power_supply_ocv2cap_simple() - find the battery capacity
  * @table: Pointer to battery OCV lookup table

include/linux/power_supply.h

@@ -349,6 +349,52 @@ struct power_supply_resistance_temp_table {
 	int resistance;	/* internal resistance percent */
 };
 
+/**
+ * struct power_supply_maintenance_charge_table - setting for maintenace charging
+ * @charge_current_max_ua: maintenance charging current that is used to keep
+ *   the charge of the battery full as current is consumed after full charging.
+ *   The corresponding charge_voltage_max_uv is used as a safeguard: when we
+ *   reach this voltage the maintenance charging current is turned off. It is
+ *   turned back on if we fall below this voltage.
+ * @charge_voltage_max_uv: maintenance charging voltage that is usually a bit
+ *   lower than the constant_charge_voltage_max_uv. We can apply this settings
+ *   charge_current_max_ua until we get back up to this voltage.
+ * @safety_timer_minutes: maintenance charging safety timer, with an expiry
+ *   time in minutes. We will only use maintenance charging in this setting
+ *   for a certain amount of time, then we will first move to the next
+ *   maintenance charge current and voltage pair in respective array and wait
+ *   for the next safety timer timeout, or, if we reached the last maintencance
+ *   charging setting, disable charging until we reach
+ *   charge_restart_voltage_uv and restart ordinary CC/CV charging from there.
+ *   These timers should be chosen to align with the typical discharge curve
+ *   for the battery.
+ *
+ * When the main CC/CV charging is complete the battery can optionally be
+ * maintenance charged at the voltages from this table: a table of settings is
+ * traversed using a slightly lower current and voltage than what is used for
+ * CC/CV charging. The maintenance charging will for safety reasons not go on
+ * indefinately: we lower the current and voltage with successive maintenance
+ * settings, then disable charging completely after we reach the last one,
+ * and after that we do not restart charging until we reach
+ * charge_restart_voltage_uv (see struct power_supply_battery_info) and restart
+ * ordinary CC/CV charging from there.
+ *
+ * As an example, a Samsung EB425161LA Lithium-Ion battery is CC/CV charged
+ * at 900mA to 4340mV, then maintenance charged at 600mA and 4150mV for
+ * 60 hours, then maintenance charged at 600mA and 4100mV for 200 hours.
+ * After this the charge cycle is restarted waiting for
+ * charge_restart_voltage_uv.
+ *
+ * For most mobile electronics this type of maintenance charging is enough for
+ * the user to disconnect the device and make use of it before both maintenance
+ * charging cycles are complete.
+ */
+struct power_supply_maintenance_charge_table {
+	int charge_current_max_ua;
+	int charge_voltage_max_uv;
+	int charge_safety_timer_minutes;
+};
+
 #define POWER_SUPPLY_OCV_TEMP_MAX 20
 
 /**
@@ -394,6 +440,10 @@ struct power_supply_resistance_temp_table {
  * @constant_charge_voltage_max_uv: voltage in microvolts signifying the end of
  *   the CC (constant current) charging phase and the beginning of the CV
  *   (constant voltage) charging phase.
+ * @maintenance_charge: an array of maintenance charging settings to be used
+ *   after the main CC/CV charging phase is complete.
+ * @maintenance_charge_size: the number of maintenance charging settings in
+ *   maintenance_charge.
  * @factory_internal_resistance_uohm: the internal resistance of the battery
  *   at fabrication time, expressed in microohms. This resistance will vary
  *   depending on the lifetime and charge of the battery, so this is just a
@@ -543,6 +593,8 @@ struct power_supply_battery_info {
 	int overvoltage_limit_uv;
 	int constant_charge_current_max_ua;
 	int constant_charge_voltage_max_uv;
+	struct power_supply_maintenance_charge_table *maintenance_charge;
+	int maintenance_charge_size;
 	int factory_internal_resistance_uohm;
 	int ocv_temp[POWER_SUPPLY_OCV_TEMP_MAX];
 	int temp_ambient_alert_min;
@@ -596,13 +648,25 @@ extern int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
 extern int
 power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table,
 				int table_len, int temp);
+extern struct power_supply_maintenance_charge_table *
+power_supply_get_maintenance_charging_setting(struct power_supply_battery_info *info, int index);
 extern void power_supply_changed(struct power_supply *psy);
 extern int power_supply_am_i_supplied(struct power_supply *psy);
 int power_supply_get_property_from_supplier(struct power_supply *psy,
 					    enum power_supply_property psp,
 					    union power_supply_propval *val);
 extern int power_supply_set_battery_charged(struct power_supply *psy);
 
+static inline bool
+power_supply_supports_maintenance_charging(struct power_supply_battery_info *info)
+{
+	struct power_supply_maintenance_charge_table *mt;
+
+	mt = power_supply_get_maintenance_charging_setting(info, 0);
+
+	return (mt != NULL);
+}
+
 #ifdef CONFIG_POWER_SUPPLY
 extern int power_supply_is_system_supplied(void);
 #else