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

[Grygorii Strashko]

On 04/25/2018 02:10 PM, Grygorii Strashko wrote:
> On 04/25/2018 01:57 PM, Florian Fainelli wrote:
> > On 04/25/2018 11:47 AM, Grygorii Strashko wrote:
> > > 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
> > > > >   ÂÂbrcmstb_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?
> >
> > You are missing me telling you the whole story, sorry I got confused,
> > but you are absolutely right these are separate lists and on
> > poweroff/shutdown only ->shutdown() is called. What I had missed in the
> > report I was submitted was that there was a .shutdown() callback being
> > added to gpio_keys.c, which of course, because it's an Android based
> > project is not in the upstream Linux kernel.
> >
> > The problem does remain valid though AFAICT. Thanks Grygorii!
>
> Thanks. But that means you should not see this problem :(
> There is devices_kset_move_last() call in really_probe() which moves probed dev
> at the end of kset, and gpio_keys should never be probed before gpio-brcmstb because
> both devm_fwnode_get_gpiod_from_child() and devm_gpio_request_one() expected to return
> -EPROBE_DEFER otherwise.
>
> Theoretically issue still might happen with suspend.

FYI https://lkml.org/lkml/2015/9/10/218

--
regards,
-grygorii