On Monday 08 of October 2012 10:48:24 MyungJoo Ham wrote:
On 8 October 2012 03:31, Rafael J. Wysocki rjw@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.venkat@linaro.org Acked-by: MyungJoo Ham myungjoo.ham@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
- 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