On 1 October 2014 21:50, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > On Wednesday, October 01, 2014 06:18:58 PM Sylwester Nawrocki wrote: >> On 01/10/14 16:41, Ulf Hansson wrote: >> > At ->probe() it's common practice for drivers/subsystems to bring their >> > devices to full power and without depending on CONFIG_PM_RUNTIME. >> > >> > We could also expect that drivers/subsystems requires their device's >> > corresponding PM domains to be powered, to successfully complete a >> > ->probe() sequence. >> > >> > Align to the behavior above, by ensuring all PM domains are powered >> > prior initialization of a generic PM domain. >> > >> > Do note, since the generic PM domain will try to power off unused PM >> > domains at late_init, there should be no increased power consumption >> > over time, but potentially during boot. >> >> Wouldn't it be a better idea to power on the power domains which are >> turned off only when CONFIG_PM_RUNTIME is not enabled ? I had a plan >> to submit a patch doing that but unfortunately this has fallen through >> the cracks. At the moment mach-exynos/pm_domains.c is not even built in >> when CONFIG_PM_RUNTIME is disabled. Yes, that's the approach I also intend to take in the next step. But, it's not that simple. Since this requires a mechanism for drivers to bring their device's PM domains into power state prior doing probe. We don't have such today. I do have some ideas about this, but I think we need to keep that as a separate discussion. >> >> I don't like the behaviour introduced in this patch to be the default, >> i.e. turning all possible power domains during boot sequence, even if >> some are not used and not needed. While we're trying to decrease the >> power consumption in any possible way this doesn't help at all. This will hit only during boot, until late_init. Unless you have a platform that keeps rebooting all the time, is this really a big worry? Still, I certainly agree that we should strive for a solution where it's possible to leave PM domains powered off at init. It's should be too hard to support this from genpd point of view, but drivers/subsystems will need some adaptations. > > Agreed (as stated before). > > And I'm wondering why that comment of mine was ignored? Sorry, if missed to comment of that. I guess I have at this point. Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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