refactor(dice): save parent context handle

Improve the restart handling of DPE. In the case of a restart
scenario where only that core is restarted which executes
the DPE client, but the core executes the DPE service
remains up and running. In this case, client needs to save
a valid context handle to be able to send commands again
to the DPE service during the new boot sequence.

BL1 saves a valid parent context handle to SDS
before passing the execution to BL2. This handle
can be used in case of a restart scenario when AP
is restarted but RSE is not. Because in that case
RSE does not save an initial context handle to SDS,
which meant to be used by AP during the boot process.

By then the very first initial context handle is
invalidated because it was already used in the
previous boot cycle by BL1.

BL2 does not need to do this, because the cold
boot starts with BL1.

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: Id14eefd2ec758f89f672af176e4f5386a397fa35
4 files changed