When the firmware wrote data to KBC/AUX output buffer, the hardware
automatically generated IRQ1/12 to notify the host. After the host read
the data, the EC received an output buffer empty (OBE) interrupt to
indicate that the next byte could be written. However, on the NPCX9M7FB,
this mechanism may cause IRQ1/12 to be missed if the firmware write new
data immediately after detecting that the output buffer is empty,
resulting in incorrect behavior.
To avoid missing IRQ1/12, the flow is changed so that it first checks
VWIRE_AVAIL to ensure no pending VW events. If no VW event is pending,
the firmware writes data to the output buffer and explicitly asserts
IRQ1/12 to notify the host. After the host reads the data and the OBE
interrupt triggers, the firmware clears IRQ1/12.
This updated sequence prevents IRQ1/12 from being lost and ensure
correct notification behavior.
Signed-off-by: Tom Chang <CHChang19@nuvoton.com>
ab7a558f19