MCSPI_CTRL_EXTCLK_SHIFT
reg &= ~(MCSPI_CTRL_EXTCLK_MSK << MCSPI_CTRL_EXTCLK_SHIFT);
reg |= extclk << MCSPI_CTRL_EXTCLK_SHIFT;
div |= ((ctrl >> MCSPI_CTRL_EXTCLK_SHIFT) & MCSPI_CTRL_EXTCLK_MSK) << 4;