On 05/08/2012 11:18 AM, Kevin Hilman wrote: > "Cousson, Benoit" <b-cousson@xxxxxx> writes: > >> On 5/8/2012 4:00 PM, Kevin Hilman wrote: >>> Jean Pihet<jean.pihet@xxxxxxxxxxxxxx> writes: >>> >>> [...] >>> >>>>>>> Yes, indeed, we should not hack the flags to fix that kind of issue. The >>>>>>> flags describe what the HW is capable of, and the EMU CD can support >>>>>>> HW_AUTO >>>>>>> and SW_WAKEUP. AFAIK, the issue with that EMU CD is that the only valid >>>>>>> next >>>>>>> power state is OFF, meaning that no retention mode is supported. So any >>>>>>> transition to idle will go to OFF and lead to a reset upon wakeup. >>>>>>> >>>>>>> That being said, being able to transition to OFF during idle is a >>>>>>> perfectly >>>>>>> valid state for most powerdomain in OMAP anyway, so we should be able to >>>>>>> restore from OFF mode smoothly. >>>>>>> >>>>>>> It looks to me that what is missing here is *just* a restore path in the >>>>>>> PMU/CTI code. But I'm probably missing some nasty details in this issue >>>>>>> :-) >>>>>> >>>>>> Although it is perfectly feasible to have a seamless transition of the >>>>>> EMU power domain, I think the PMU counters will not be accurate >>>>>> anymore since they stop counting events when going to OFF and re-start >>>>>> after the state restore. >>>>> >>>>> >>>>> Good point, but I think the PMU might still works fine because located >>>>> inside the MPU domain. AFAIR, only the path to access the PMU and the CTI is >>>>> going to OFF and thus will be reset. >>>> >>>> Ever better point ;p Thanks for the precision. >>>> In any case my point was: can we allow the EMU CD to go OFF or prevent >>>> it from doing so? We need to answer that question first. >>>> >>> >>> The idea I've suggested is to use runtime PM for this. As long as the >>> PMU is in use, it will be runtime PM enabled (and not allowed to go into >>> HWSUP idle.) When it is not used, it will be allowed to HWSUP idle, and >>> then be reset. The next time it is needed, the runtime resume will need >>> to do a full re-init. >> >> Oh, but does that mean that this driver is not pm_runtime adapted yet? >> > > Actually, it is. Ming Lei has done it. > > Currently, Will has collected this[1] and is waiting (patiently) for us > to produce a real fix that doesn't kill PM in the process. I had to make a couple mods to Ming's patches but I do have something working now that _should_ not break PM. However, per my previous email (in response to Benoit's) I am struggling with the definition of the CLKDM_CAN_XXXXXX_AUTO flags to know the correct way to fix this. I was going to send out my patches, but I wanted to get some more feedback on this first. Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
