mmc_set_signal_voltage
if (!mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_330))
else if (!mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180))
else if (!mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120))
if (mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180))
int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_330);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120);
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
if (mmc_set_signal_voltage(host, old_signal_voltage))