ACPI: Add support for runtime config TDP down

The required power MSRs are mirrored in MCHBAR so
it is possible to configure TDP at runtime via ASL.

This adds the required fields and a set of methods to
configure "TDP down" and "TDP nominal".  It explicitly
does not support "TDP up" at the moment.

PSSS: method is added to assist in searching the _PSS
table for the appropriate entry that corresponds to the
desired max non-turbo ratio.

STND: Set TDP Down from Nominal.  This will limit CPU to
the TDP down configuration by sequencing the required
changes in the right order.

STDN: Set TDP Nominal from Down.  This will set the CPU
back to nominal configuration by sequencing the required
changes in the correct (reverse) order.

This does not introduce any functional changes and must
be paired with additional changes to be useful.

The current configured TDP can be checked to see that
the transition to/from a desired level is successful.

> mmio_read8 0xfed15f50
0x00  # TDP-Nominal

> mmio_read8 0xfed15f50
0x01  # TDP-Down

Change-Id: I31a2f30cc9d134cc5eee980ae9288ae45e71c6e6
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/1344
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

0 files changed, 0 insertions, 0 deletions