Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Microchip Technology/ATSAMV71J20/HSMCI/SDCR#0x0
SDCBUS=_1, SDCSEL=SLOTA
SD/SDIO Card Register
SDCard/SDIO Slot
0 (SLOTA): Slot A is selected.
SDCard/SDIO Bus Width
0 (_1): 1 bit
2 (_4): 4 bits
3 (_8): 8 bits
https://github.com/cmsis-svd/cmsis-svd-data