polling/interrupt-driven fallback and instead use polling only during
boot and pure interrupt-driven mode after boot. Polled mode could be
relegated completely to a legacy role if we could enable interrupts
during boot. Polled mode can be forced after boot by setting
debug.acpi.ec.polled="1", i.e. if there are timeouts.
- Use polling only during boot, shutdown, or if requested by the user.
Otherwise, use a generation count of GPEs, incremented atomically. This
prevents an old status value from being used if the EC is really slow
and the same condition (i.e. multiple IBEs for a write transaction) is
being checked.
- Check for and run the query handler directly if the SCI bit is set in
the status register during boot. Previously, the query handler wouldn't
run until interrupts were finally enabled late in boot.
- During boot and after starting a command, check if the event appears
to already have occurred before we even start waiting. If so, it's
possible the EC is very slow and we might accept an old status value.
Print a warning in this case. Once we've booted, interrupt-driven mode
should work just fine but polled mode could be unreliable. There's not
much more we can do about this until interrupts are enabled during boot.
- In the above case, we also do one final check if the interrupt-driven
mode gets a timeout. If the status is complete, it will force the
system back into polled mode since interrupt mode doesn't work. For
polled mode during boot, if the status appears to be already complete
before beginning the check loop, it waits 10 us before actually checking
the status, just in case the EC is really slow and hasn't gotten to work
on the new request yet.
- Use upper-case hex for the _Qxx method
- Use device_printf for errors, don't hide them under verbose
- Increase default total timeout to 750 ms and decrease polling interval
to 5 us.
- Don't pass the status value via the softc. Just read it directly.
- Remove the mutex. We use the sx lock for transaction serialization
with the query handler.
- Remove the Intel copyright notice as no code of theirs was ever
present in this file (verified against rev 1.1)
- Allow KTR module-only builds for ease of testing
Thanks to jkim and Alexey Starikovskiy for helpful discussions and testing.
Approved by: re
MFC after: 2 weeks
b50224d3f9