REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4427
1. Since UART speed is slower than CPU, BIOS need to check the write
buffer is empty, to avoid overwrite the buffer content.
2. LPSS UART might disable MMIO space for Windows debug usage during
ExitBootServices event. BIOS need to avoid access the MMIO space
after ExitBootServices.
Cc: Guo Dong <guo.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Sean Rhodes <sean@starlabs.systems>
Cc: James Lu <james.lu@intel.com>
Reviewed-by: Gua Guo <gua.guo@intel.com>
Signed-off-by: PaytonX Hsieh <paytonx.hsieh@intel.com>
PaytonX Hsieh