Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32l4+/STM32L4R5/GFXMMU/SR#0x0
Graphic MMU status register
Buffer 0 overflow flag
Buffer 1 overflow flag
Buffer 2 overflow flag
Buffer 3 overflow flag
AHB master error flag
https://github.com/modm-io/cmsis-svd-stm32