The PMC EPOC register indicates which external crystal oscillator is
connected to the PCH. This frequency is important for determining the
IP clock of internal PCH devices.
Add definitions that allow this register to be read and extract the
crystal frequency, and a helper function to extract and return this
as the defined enum.
BUG=b:146482091
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Change-Id: I959fe507f3dbf93b6176b333a9e725ed09f56328
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40887
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
526880754f