There are two communication scheme that have been enabled to communicate
with Secure Proxy in TI.
a) A full fledged prioritized communication scheme, which involves upto
5 threads from the perspective of the host software
b) A much simpler "lite" version which is just a two thread scheme
involving just a transmit and receive thread scheme.
The (a) system is specifically useful when the SoC is massive
involving multiple processor systems and where the potential for
priority inversion is clearly a system usecase killer. However, this
comes with the baggage of significant die area for larger number of
instances of secure proxy, ring accelerator and backing memories
for queued messages. Example SoCs using this scheme would be:
AM654[1], J721E[2], J7200[3] etc.
The (b) scheme(aka the lite scheme) is introduced on smaller SoCs
where memory and area concerns are paramount. The tradeoff of
priority loss is acceptable given the reduced number of processors
communicating with the central system controller. This brings about
a very significant area and memory usage savings while the loss of
communication priority has no demonstrable impact. Example SoC using
this scheme would be: AM642[4]
While we can detect using JTAG ID and conceptually handle things
dynamically, adding such a scheme involves a lot of unused data (cost
of ATF memory footprint), pointer lookups (performance cost) and still
due to follow on patches, does'nt negate the need for a different
build configuration. However, (a) and (b) family of SoCs share the
same scheme and addresses etc, this helps minimize our churn quite a
bit
Instead of introducing a complex data structure lookup scheme, lets
keep things simple by first introducing the pieces necessary for an
alternate communication scheme, then introduce a second platform
representing the "lite" family of K3 processors.
NOTE: This is only possible since ATF uses just two (secure) threads
for actual communication with the central system controller. This is
sufficient for the function that ATF uses.
The (a) scheme and the (b) scheme also varies w.r.t the base addresses
used, even though the memory window assigned for them have remained
consistent. We introduce the delta as part of this change as well.
This is expected to remain consistent as a standard in TI SoCs.
References:
[1] See AM65x Technical Reference Manual (SPRUID7, April 2018)
for further details: https://www.ti.com/lit/pdf/spruid7
[2] See J721E Technical Reference Manual (SPRUIL1, May 2019)
for further details: https://www.ti.com/lit/pdf/spruil1
[3] See J7200 Technical Reference Manual (SPRUIU1, June 2020)
for further details: https://www.ti.com/lit/pdf/spruiu1
[4] See AM64X Technical Reference Manual (SPRUIM2, Nov 2020)
for further details: https://www.ti.com/lit/pdf/spruim2
Signed-off-by: Nishanth Menon <nm@ti.com>
Change-Id: I697711ee0e6601965015ddf950fdfdec8e759bfc
Nishanth Menon
7f323eb2df