On 22 October 2015 at 02:54, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > On Tuesday, October 20, 2015 06:21:55 PM Tomeu Vizoso wrote: >> On 20 October 2015 at 18:04, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Tue, 20 Oct 2015, Mark Brown wrote: >> > >> >> On Tue, Oct 20, 2015 at 10:40:03AM -0400, Alan Stern wrote: >> >> >> >> > Furthermore, that applies only to devices that use synchronous suspend. >> >> > Async suspend is becoming common, and there the only restrictions are >> >> > parent-child relations plus whatever explicit requirements that drivers >> >> > impose by calling device_pm_wait_for_dev(). >> >> >> >> Hrm, this is the first I'd noticed that feature though I see the initial >> >> commit dates from January. >> > >> > Async suspend and device_pm_wait_for_dev() were added in January 2010, >> > not 2015! >> > >> >> It looks like most of the users are PCs at >> >> the minute but we should be using it more widely for embedded things, >> >> there's definitely some cases I'm aware of where it will allow us to >> >> remove some open coding. >> >> >> >> It does seem like we want to be feeding dependency information we >> >> discover for probing way into the suspend dependencies... >> > >> > Rafael has been thinking about a way to do this systematically. >> > Nothing concrete has emerged yet. >> >> This iteration of the series would make this quite easy, as >> dependencies are calculated before probes are attempted: >> >> https://lkml.org/lkml/2015/6/17/311 > > Well, if you know how to represent "links" between devices, the mechanism > introduced here doesn't really add much value, because in that case the > core knows what the dependencies are in the first place and can only > defer the probes that have to be deferred. By "here" you mean what you are proposing for ordering device suspends, or on-demand probing? If you meant that probing on-demand is unneeded if we already have dependency information, I agree with you and that's why I only pushed forward on-demand, as the approach linked above introduced some duplication when inferring the dependencies. Maybe that could be avoided without too much refactoring. In any case, Thierry mentioned the other day in #tegra that one could also collect dependency information as a follow up to the on-demand series by calling device_depend() or such instead of of_device_probe(). Regards, Tomeu > Thanks, > Rafael > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
