power: supply: bq25890_charger: Read back the current battery voltage

The BQ2589x family has the capability of reading the current battery voltage.

Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Angus Ainslie (Purism) <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/bq25890_charger.c

···
 		val->intval = bq25890_find_val(bq->init_data.iterm, TBL_ITERM);
 		break;
 
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		ret = bq25890_field_read(bq, F_SYSV); /* read measured value */
+		if (ret < 0)
+			return ret;
+
+		/* converted_val = 2.304V + ADC_val * 20mV (table 10.3.15) */
+		val->intval = 2304000 + ret * 20000;
+		break;
+
 	default:
 		return -EINVAL;
 	}
···
 	POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE,
 	POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE_MAX,
 	POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
 };
 
 static char *bq25890_charger_supplied_to[] = {