rk3328_iomux_set_bias
rk3328_iomux_set_bias(sc, bank, idx, GRF_GPIO_P_CTL_Z);
rk3328_iomux_set_bias(sc, bank, idx, GRF_GPIO_P_CTL_PULLUP);
rk3328_iomux_set_bias(sc, bank, idx, GRF_GPIO_P_CTL_PULLDOWN);