Hi, I have a bug to report with the serial I/O protocol. Using the SetAttributes function to change the timeout initially works, but after a short amount of time the timeout gets reset to 173 microseconds.

I believe this is likely due to the implementation of the simple text input protocol, which alters the serial timeout:
https://github.com/tianocore/edk2/blob/e1e7306b54147e65cb7347b060e94f336d4a82d2/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c#L549

I've created a full example here:
https://github.com/nicholasbishop/edk2/commit/d6087f863a48f3c7812f47ea21d5d673adb8d754

The example sets the timeout to 1s which works correctly, then sleeps for 1s and reads the timeout value again. The timeout is now 173ms.