Shilpasri G Bhat [off-list ref] writes:

Add OPAL_MSG_OCC message definition to opal_message_type to receive
OCC events like reset, load and throttled. Host performance can be
affected when OCC is reset or OCC throttles the max Pstate.
We can register to opal_message_notifier to receive OPAL_MSG_OCC type
of message and report it to the userspace so as to keep the user
informed about the reason for a performance drop in workloads.

The reset and load OCC events are notified to kernel when FSP sends
OCC_RESET and OCC_LOAD commands.  Both reset and load messages are
sent to kernel on successful completion of reset and load operation
respectively.

How is this done on OpenPower systems? Explanation involving just what
OPAL does is likely better, rather than explaining in context of FSP,
which Linux has no real knowledge of (OPAL provides all abstraction of
it).