38940b8f25
According to the manual of SiFive U74, implement a new method to flush the entire L2 cache by using the Zero Device. After testing, 512KB is the critical point between the old and new way. It's better to use sifive_ccache_flush_entire function while data size is larger than cache size. Or it will improve more at 512KB when you know what you are doing. Signed-off-by: Windsome Zeng <windsome.zeng@starfivetech.com>