Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32L4x1/DMA1/CSELR#0x0
channel selection register
DMA channel 1 selection
DMA channel 2 selection
DMA channel 3 selection
DMA channel 4 selection
DMA channel 5 selection
DMA channel 6 selection
DMA channel 7 selection
https://github.com/cmsis-svd/cmsis-svd-data