* Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> [171108 00:47]: > On Wednesday, November 8, 2017 1:28:24 AM CET Florian Fainelli wrote: > > 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. > > I see, thanks for explaining that clearly. > > Then it looks like that there needs to be a way for the "cached" state to be > invalidated and the question is what that way should be and how it is going to > be triggered. Yeah seems like that issue needs to be solved at the pinctrl level even if the drivers were using a generic state for the context lost for figuring out when to do it. Regards, Tony -- 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
