Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32L4S9/DSI/DSI_LPCR#0x0
DSI Host LTDC Polarity Configuration Register
Data Enable Polarity
VSYNC Polarity
HSYNC Polarity
https://github.com/cmsis-svd/cmsis-svd-data