SDMMC_CLKEN_LOW_PWR
clk_en_a |= SDMMC_CLKEN_LOW_PWR << slot->id;
const u32 clken_low_pwr = SDMMC_CLKEN_LOW_PWR << slot->id;
clk_en_a &= ~(SDMMC_CLKEN_LOW_PWR << slot->id);