ec/acpi: add mechanisms to clear EC output queue

EC's output could be considered as a queue, and sometimes (observed on
Thinkpad T400s during cold boot) a few (only one observed) garbage bytes
may detained in such queue after power up. Those garbage bytes should be
checked and discarded first before real interactions, otherwise they may
disrupt the interaction during EC's enablement, causing a locked rfkill.

Change-Id: Iee031306c02f5211a4512c6b4ec90f7f0db196ae
Signed-off-by: Bill XIE <>
Tested-by: build bot (Jenkins) <>
Reviewed-by: Patrick Rudolph <>
2 files changed