On 10/30/2012 10:10 AM, Felipe Balbi wrote: > Hi, > > On Tue, Oct 30, 2012 at 09:16:34AM -0500, Jon Hunter wrote: >> Hi Felipe, >> >> On 10/30/2012 02:09 AM, Felipe Balbi 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. >>> 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 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. >> 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. Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
