Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32u5/STM32U535/SDMMC/SDMMC_IDMACTRLR#0x0
DMA control register
IDMA enable This bit can only be written by firmware when DPSM is inactive (DPSMACT = 0).
Buffer mode selection. This bit can only be written by firmware when DPSM is inactive (DPSMACT = 0).
https://github.com/modm-io/cmsis-svd-stm32