power: supply: ab8500: Respect charge_restart_voltage_uv

The battery info contains a voltage indicating when the voltage
is so low that it is time to restart the CC/CV charging.
Make the AB8500 respect and prioritize this setting over the
hardcoded 95% threshold.

Break out the check into its own function and add some safeguards
so we do not run into unpredictable side effects.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/ab8500_chargalg.c

@@ -1216,6 +1216,34 @@ static void ab8500_chargalg_external_power_changed(struct power_supply *psy)
 		queue_work(di->chargalg_wq, &di->chargalg_work);
 }
 
+/**
+ * ab8500_chargalg_time_to_restart() - time to restart CC/CV charging?
+ * @di: charging algorithm state
+ *
+ * This checks if the voltage or capacity of the battery has fallen so
+ * low that we need to restart the CC/CV charge cycle.
+ */
+static bool ab8500_chargalg_time_to_restart(struct ab8500_chargalg *di)
+{
+	struct power_supply_battery_info *bi = di->bm->bi;
+
+	/* Sanity check - these need to have some reasonable values */
+	if (!di->batt_data.volt_uv || !di->batt_data.percent)
+		return false;
+
+	/* Some batteries tell us at which voltage we should restart charging */
+	if (bi->charge_restart_voltage_uv > 0) {
+		if (di->batt_data.volt_uv <= bi->charge_restart_voltage_uv)
+			return true;
+		/* Else we restart as we reach a certain capacity */
+	} else {
+		if (di->batt_data.percent <= AB8500_RECHARGE_CAP)
+			return true;
+	}
+
+	return false;
+}
+
 /**
  * ab8500_chargalg_algorithm() - Main function for the algorithm
  * @di:		pointer to the ab8500_chargalg structure
@@ -1459,7 +1487,7 @@ static void ab8500_chargalg_algorithm(struct ab8500_chargalg *di)
 		fallthrough;
 
 	case STATE_WAIT_FOR_RECHARGE:
-		if (di->batt_data.percent <= AB8500_RECHARGE_CAP)
+		if (ab8500_chargalg_time_to_restart(di))
 			ab8500_chargalg_state_to(di, STATE_NORMAL_INIT);
 		break;