> On Monday 08 of October 2012 10:48:24 MyungJoo Ham wrote: > > > On 8 October 2012 03:31, Rafael J. Wysocki <r...@sisk.pl> wrote: > > > > On Thursday 04 of October 2012 14:58:33 Rajagopal Venkat wrote: > > > >> Add devfreq suspend/resume apis for devfreq users. This patch > > > >> supports suspend and resume of devfreq load monitoring, required > > > >> for devices which can idle. > > > >> > > > >> Signed-off-by: Rajagopal Venkat <rajagopal.ven...@linaro.org> > > > >> Acked-by: MyungJoo Ham <myungjoo....@samsung.com> > > > > > > > > Well, I wonder if this may be tied in to the runtime PM framework, so > > > > that, > > > > for example, pm_runtime_suspend() will automatically suspend devfreq on > > > > success (and the runtime resume of the device will resume devfreq)? > > > > > > That's a good idea. If you agree, we can handle this as separate patch on > > > top this patchset. > > Sure. > > > I guess implementing the idea may be not so obvious; thus, seperating > > the patchset would be appropriate. > > > > When we implement the idea, we may need to implement at the > > pm_runtime core. Because devfreq->dev is a child of the target dev, not > > a parent, runtime-pm event of the target dev does not automatically > > invoke a cascaded action on the devfreq->dev. > > I'm not exactly sure what you mean, care to explain?
When a device "p" creates devfreq, devfreq->dev->parent = p. And, devfreq's functions need to react to the "p"'s runtime-pm events. However, when "p"'s runtime-pm-suspend is being invoked, devfreq->dev's runtime-pm-suspend won't be automatically invoked. Thus, we will need a mechanism that invokes devfreq->dev's runtime-pm callbacks when p's runtime-pm is invoked. (at the runtime-pm core) Or A mechanism that one can notify others (including its children) when the one's runtime-pm is invoked. (probably at the runtime-pm core, too) Without such support, it appears that the current implementation (calling runtime-pm suspend/resume equivalent devfreq functions manually at device drivers) seems to be inevitable. Anyway, if devfreq->dev is a parent of "p", runtime-pm core will do the required task automatically; however, it isn't and I don't think it'd be appropriate. > > > Maybe either > > 1) capability to allow a child to monitor the power state of a parent > > (I remember Inki Dae once suggested to add notifiers at runtime-pm, but > > it seems to be not merged) > > or > > 2) letting runtime-pm be aware of devfreq > > (doesn't feel alright with this??) > > is required? > > I'm not a big fan of notifiers, so I'd prefer to avoid using them, if > possible. > > Thanks, > Rafael > > > -- > I speak only for myself. > Rafael J. Wysocki, Intel Open Source Technology Center. > Cheers, MyungJoo
