Hi, On Wed, Oct 31, 2012 at 05:15:02AM -0500, Jon Hunter wrote: > >>>> its bit of an issue to take care. How do you ensure that GPIO > >>>> does idle on SOC idle C-state attempts in such cases. Today that > >>>> job is done by omap_gpio_[prepare/resume]_for_idle. > >>> > >>> that's only there because we pm_runtime_get_sync() on gpio_request() and > >>> pm_runtime_put_sync() only on gpio_free(). > >>> > >>> That's the problem IMHO. And that's easy enough to 'fix': > >>> > >>> call pm_runtime_mark_last_busy(); pm_runtime_put_sync_autosuspend(); > >>> also on gpio_request() and pm_runtime_get_sync() on gpio_free(). > >> > >> Sounds like a good approach. I have been discussing with Kevin and I > >> need to look more at the resume handler as we are working around some > >> old issues in there and with this approach the resume following idle > >> will be delayed and we were not sure if there could be any implications > >> for omap2. I am hoping not, but we need to look into this. > >> > >> So I am wondering if we should just take Tim's original proposal for now > >> and then I will look into improving this long term. I really need to > >> clean-up the suspend/resume stuff for gpio and so may be we can make > >> that a separate change. What do you think? > > > > that'll cause a regression right ? > > Sorry, not sure I follow. $SUBJECT will prevent core idle. > >>> The difficult part, IMHO, is to figure out what's a good autosuspend > >>> timeout to use. Some GPIO lines are used as IRQ lines on some devices, > >>> that means that the GPIO will be periodically triggered and, depending > >>> on our timeout, we will either loose IRQs or prevent power domain from > >>> idling. We could figure out a way to let board code to choose what it > >>> wants on a per-bank basis (maybe some extra DT attribute). > >> > >> I have also been bending Kevin's ear on this, this week and we were > >> wondering if we should make the default 0 for now as this will have the > > > > I believe you mean -1 here ;-) > > I did mean 0, so that it will autosuspend right away. Basically, it will > behave like today, however, will allow people to change the timeout. I yeah, that's the -1 timeout, it disables pm timer and all pm_runtime_*_autosuspend() will act as pm_runtime_*(). > did not wish to make it -1 as then suspend/resume would not be exercised > and so people would need to change it via the sysfs to exercise deep > power states on the device. why won't be exercised ? > >> same behaviour that we have today but would allow Tim to customise via > >> the sysfs for his specific app. > > > > sysfs might be too late for his platform. What if he needs NFS root > > (just wondering, not sure about his use case) ? > > His use case was for SPI (see the original changelog). That's a good > point, but I am wondering if we can live with that for now. fair enough, but it's possible we will cause regressions. At least with current version of $SUBJECT, I guess. -- balbi
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