Acer 3623 with acpi version 20070320

[Ted Lindgreen]

Until revision 1.68 of acpi_ec.c ACPI worked on my Acer 3623
laptop, although lots of AE_NO_HARDWARE_RESPONSE messages were
produced.
I used a custom DSDT file, and a few patches to suppress
the error messages.

Starting with revision 1.69 of acpi_ec.c things like battery
status stopped working. The import of 20070320 made no change.

I found that the Acer does not like the EC_GET_CSR in EcWaitEvent to
happen too quickly after an EC_SET_DATA or EC_SET_CSR command.
Polling repeatedly makes thing worse as I found out playing with the
tunables debug.acpi.ec.poll_time and debug.acpi.ec.timeout: the
system freezes while slowly spitting out AE_NO_HARDWARE_RESPONSE
messages.

What did improve things was to insert a delay before EC_GET_CSR in
EcWaitEvent. There is already code to do that, but it is
disabled by #if 0 and the delay is coupled to EC_POLL_DELAY.

Playing with a tunable delay here showed that with
   AcpiOsStall( 2200 );
the number of AE_NO_HARDWARE_RESPONSE messages started dropping.
With 2300 us delay these messages occur only occasionally, and
battery-status works again. With 2500 us delay there are no
more error messages and everything works fine.

I have debug.acpi.ec.poll_time and debug.acpi.ec.timeout back to
default, and debug.acpi.ec.burst: 1.
I also found that now I do not need the custom DSDT file anymore.

regards,
-- ted