[...]

quoted

I understand the arguments for using PC vs OSI and agree with it. But
what in PSCI is against Linux knowing when the last core is powering
down when the PSCI is configured to do only Platform Cordinated.

Nothing :D. But knowing the evolution and reasons for adding OSI in the
PSCI specification and having argued about benefits of OSI over PC for
years and finally when we have it in mainline, this argument of using
PC for exact reasons why OSI evolved is something I can't understand
and I am confused.

quoted

There should not be any objection to drivers knowing when all the cores
are powered down, be it reference counting CPU PM notifications or using
a cleaner approach like this where GendPD framwork does everything
cleanly and gives a nice callback. ARM architecture allows for different
aspects of CPU access be handled at different levels. I see this as an
extension of that approach.

One thing that was repeatedly pointed out during OSI patch review was no
extra overhead for PC mode where firmware can make decisions. So, just
use OSI now and let us be done with this discussion of OSI vs PC. If PC
is what you think you need for future, we can revert all OSI changes and
start discussing again :-)

Just to make it clear, I fully agree with you in regards to overhead
for PC-mode. This is especially critical for ARM SoCs with lots of
cores, I assume.

However, the overhead you refer to, is *only* going to be present in
case when the DTS has the hierarchical CPU topology description with
"power-domains". Because, that is *optional* to use, I am expecting
only those SoC/platforms that needs to manage last-man activities to
use this layout, the others will remain unaffected.

That said, does that address your concern?

Kind regards
Uffe

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