bq27x00_battery: Fixup nominal available capacity reporting

We should not not report nominal available capacity if battery is not
calibrated, as we don't want to represent bogus values in the sysfs and
confuse userland.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

drivers/power/bq27x00_battery.c

@@ -230,6 +230,14 @@ static int bq27x00_battery_read_charge(struct bq27x00_device_info *di, u8 reg)
  */
 static inline int bq27x00_battery_read_nac(struct bq27x00_device_info *di)
 {
+	int flags;
+	bool is_bq27500 = di->chip == BQ27500;
+	bool is_higher = bq27xxx_is_chip_version_higher(di);
+
+	flags = bq27x00_read(di, BQ27x00_REG_FLAGS, !is_bq27500);
+	if (flags >= 0 && !is_higher && (flags & BQ27000_FLAG_CI))
+		return -ENODATA;
+
 	return bq27x00_battery_read_charge(di, BQ27x00_REG_NAC);
 }