To avoid reading stale data when using mmap on ARM64:

Use msync: Call msync(ptr, size, MS_SYNC | MS_INVALIDATE) to flush and invalidate caches.

Use Memory Barriers: Add asm volatile ("dsb sy" ::: "memory"); to enforce memory synchronization.

Open with O_SYNC: Use open("/dev/mem", O_RDWR | O_SYNC) for synchronous memory access.

Configure Uncached Mapping: Ensure mmap maps the buffer with uncached attributes (MAP_SHARED).

Check DMA Coherence: Use DMA-coherent memory for hardware buffers, if supported.

These methods ensure timely updates from the hardware buffer to the mapped memory.