When ACPI was originally merged for arm64 it had only been tested on
emulators and not on real physical platforms and no platforms were
relying on it.  This meant that there were concerns that there might be
serious issues attempting to use it on practical systems so it had a
dependency on EXPERT added to warn people that it was in an early stage
of development with very little practical testing.  Since then things
have moved on a bit.  We have seen people testing on real hardware and
now have people starting to produce some platforms (the most prominent
being the 96boards Cello) which only have ACPI support and which build
and run to some useful extent with mainline.

This is not to say that ACPI support or support for these systems is
completely done, there are still areas being worked on such as PCI, but
at this point it seems that we can be reasonably sure that ACPI will be
viable for use on ARM64 and that the already merged support works for
the cases it handles.  For the AMD Seattle based platforms support
outside of PCI has been fairly complete in mainline a few releases now.

This is also not to say that we don't have vendors working with ACPI who
are trying do things that we would not consider optimal but it does not
appear that the EXPERT dependency is having a substantial impact on
these vendors.

Given all this it seems that at this point the EXPERT dependency mainly
creates inconvenience for users with systems that are doing the right
thing and gets in the way of including the ACPI code in the testing that
people are doing on mainline.  Removing it should help our ongoing
testing cover those platforms with only ACPI support and help ensure
that when ACPI code is merged any problems it causes for other users are
more easily discovered.
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Graeme Gregory <graeme.gregory@linaro.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Al Stone <ahs3@redhat.com>
Acked-by: Hanjun Guo <hanjun.guo@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Roy Franz <roy.franz@hpe.com>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>