selector); else selector = -1; The list_voltage call here takes the selector got from set_voltage callback. Thus adding 0x2f to the index in pcf50633_regulator_list_voltage looks wrong to me. e.g. If min_uV < 1.8V, pcf50633_regulator_set_voltage sets 0 to selector. For this case, adding 0x2f to the index in pcf50633_regulator_list_voltage is correct. However, if min_uV == 1.8V, pcf50633_regulator_set_voltage sets 0x2f to selector. Adding 0x2f to the index in pcf50633_regulator_list_voltage in this case is wrong. What this patch does is: The minimal voltage setting for AUTOOUT is 0x2f. Thus for the case min_uV < 1.8, set the voltage setting to 1.8V by writting 0x2f to AUTOOUT register and set selector = 0x2f. So we don't write the rserved range to AUTOOUT register. Which means the possible range of AUTOOUT register value is 0x2f ~ 0xff. We have no problem in regulator_get_voltage. Since we won't write 0~0x2e to AUTOOUT register, we have no problem converting the bits we read to voltage. The equation in auto_voltage_value works fine. For list_voltage, we need to take into account the case selector is 0 ~ 0x2e because the regulator core assumes the selector is starting from 0. This patch returns 0 for the cases selector is 0 ~ 0x2e, which means "this selector code can't be used on this system". The regulator core iterates from 0 to n_voltages to find the small voltage in the specific range. The n_voltages settings for AUTOOUT should be 128 now, including the reserved range of AUTOOUT. Signed-off-by: Axel Lin Acked-by: Lars-Peter Clausen Signed-off-by: Mark Brown Ò)Îo’