RTSX_CLK_DIVIDE_MASK
RTSX_BITOP(sc, RTSX_SD_CFG1, RTSX_CLK_DIVIDE_MASK, clk_divider);
rtsx_write(sc, RTSX_SD_CFG1, RTSX_CLK_DIVIDE_MASK, RTSX_CLK_DIVIDE_0);
rtsx_write(sc, RTSX_SD_CFG1, RTSX_CLK_DIVIDE_MASK, RTSX_CLK_DIVIDE_128);
rtsx_write(sc, RTSX_SD_CFG1, RTSX_CLK_DIVIDE_MASK, RTSX_CLK_DIVIDE_128);