On 11/07/2017 04:23 PM, Rafael J. Wysocki wrote: > On Tuesday, November 7, 2017 5:00:06 PM CET Tony Lindgren wrote: >> * Florian Fainelli <f.fainelli@xxxxxxxxx> [171104 17:21]: >>> >>> >>> On 11/04/2017 05:25 AM, Rafael J. Wysocki wrote: >>>> On Friday, November 3, 2017 6:33:53 PM CET Tony Lindgren wrote: >>>>> * Florian Fainelli <f.fainelli@xxxxxxxxx> [171103 17:04]: >>>>>> On 11/03/2017 09:11 AM, Tony Lindgren wrote: >>>>>> The pinctrl provider is losing its state, hence these two patches. >>>>> >>>>> OK >>>>> >>>>>>> Anyways, the context lost flag should be managed in the PM core for >>>>>>> the device, so adding linux-pm and Rafael to Cc. >>>>>> >>>>>> I don't think it's that simple but sure, why not. >>>>> >>>>> Just having bool context_lost in struct dev_pm_info would probably >>>>> be enough to allow drivers to deal with it. This flag could then >>>>> be set for a device by power domain related code that knows if >>>>> context got lost. >>>> >>>> Something like: if the driver sees "context_lost" set, it should restore >>>> the context to the device from memory? >>> >>> That is what is being proposed here, except that the actual mechanism >>> where this matters needs to be in the core pinctrl code, otherwise the >>> state (context) is not restored due to a check that attempts not to >>> (re)apply a previous state. >>> >>>> >>>> But the it would also need to save the context beforehand, so why not to >>>> restore it unconditionally on resume? >>> >>> That's what my original attempts did here: >>> >>> https://patchwork.kernel.org/patch/9598969/ >>> >>> but Linus rightfully requested this to be done differently, hence this >>> attempt now to solve it in a slightly more flexible way based on DT >>> properties. >> >> For runtime PM, restoring the state constantly is unnecessary and not >> good for battery life. The logic can be just: >> >> 1. Device driver runtime PM suspend saves the state when needed >> >> 2. Device driver runtime PM resume checks if context_lost was set by >> the bus or power domain code >> >> 3. If context was lost, device driver restores the state, or in some >> cases may need re-run the driver register init related parts >> to bring the driver back up, then clears the context_lost flag >> >> How about something like the following patch? So far only compile >> tested with CONFIG_PM enabled. If that looks like the way to go, >> I'll test it properly and add some comments for the functions and >> post a proper patch :) > > Honestly, I'm not sure. > > I'd rather have a context_lost flag to start with and see how/if > drivers will use that before adding any common infra for handling > this. I am afraid we are being slightly side tracked here on this context_loss flag, because the crux of the problem is not whether a driver knows or not when it loses state, it's more than the pinctrl core refuses to re-apply the same state upon resumption even when the consumer driver tells it to, because it has not seen a transition (consider it as a stale software cache of the state), and there is only one state defined. I don't particularly care how its gets solved, at the generic device driver model or at the pinctrl level, but I think the pinctrl code needs to change in that regard no matter what we do, because right now, if you call pinctrl_select_state() in your driver's resume function, and there is only one state defined, nothing happens, that's a problem. -- Florian -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
