Still having issues with tracking down how this is supposed to work using F746G-Discovery board, F7V1.11.0 CubeMX, with the board configured to use FreeRTOS, FatFs, SDMMC, and DMA. Everything is fine up to f_close, after which the system times out and the close fails.
Reading some other examples of DMA+FreeRTOS, I see that the callbacks are registered using HAL_DMA_RegisterCallback which is missing in the initialization. I also notice that the callbacks are not being executed which is why the timeout. Is this something that needs to be entered as User code? If so, with respect to the discovery board noted, what would that look like?