[...] > > 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. > > > 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
