Re: Lack of suspend/resume/shutdown ordering between GPIO providers and consumers

[Grygorii Strashko]

On 04/25/2018 01:29 PM, Florian Fainelli wrote:
> On 04/25/2018 11:06 AM, Grygorii Strashko wrote:
> > On 04/24/2018 05:58 PM, Florian Fainelli wrote:
> > > Hi Linus, Rafael, all
> > >
> > > Our GPIO controller driver: gpio-brcmstb.c has a shutdown callback which
> > > gets invoked when the system is brought into poweroff aka S5. So far so
> > > good, except that we also wish to use gpio_keys.c as a possible wake-up
> > > source, so we may have a number of GPIO pins declared as gpio-keys that
> > > allow the system to wake-up from deep slumber.
> > >
> > > Recently we noticed that we could easily get into a state where
> > > gpio-brcmstb.c::brcmstb_gpio_shutdown() gets called first, and then
> > > gpio_keys.c::gpio_keys_suspend() gets called later, which is too late to
> > > have the enable_irq_wake() call do anything sensible since we have
> > > suspend its parent interrupt controller before. This is completely
> > > expected unfortunately because these two drivers are both platform
> > > device instances with no connection to one another except via Device
> > > Tree and the use of the GPIOLIB APIs.
> >
> > You can take a look at device_link_add() and Co.
>
> OK, though that requires a struct device references, so while I could
> certainly resolve the device_node -> struct device that corresponds to
> the GPIO provider , that poses a number of issues:
>
> - not all struct device_node have a corresponding struct device
> reference (e.g: clock providers, interrupt controllers, and possibly
> other custom drivers), though in this case, they most likely do have one
>
> - resolving a struct device associated with a struct device_node is
> often done in a "bus" specific way, e.g: of_find_device_by_node(), so if
> the GPIO provider is e.g: i2c_device, pci_device etc. etc. this might
> not work that easily
>
> I think this is what Dmitry just indicated in his email as well.
>
> > But it's little bit unclear what exactly you have issue with:
> > - shutdown
> > - suspend
> >
> > above are different (at least as it was before) and gpio-brcmstb.c
> >  Âbrcmstb_gpio_shutdown() should not be called as part of suspend !?
> > may be you mean brcmstb_gpio_suspend?
>
> The issue exists with shutdown (through the use of "poweroff"), that is
> confirmed, but I cannot see how it does not exist with any suspend state
> as well, for the same reason that the ordering is not strictly enforced.

Sry, but it still required some clarification :( - poweroff calls
device_shutdown() which, in turn, should not call .suspend(), so
how have you got both .shutdown() and .suspend() callbacks called during
poweroff? Am I missing smth?

Note. Suspend and shutdown uses different dev lists:
- shutdown uses kset
- suspend uses dpm_list

--
regards,
-grygorii