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

[Florian Fainelli <f.fainelli@gmail.com>]

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
>>>   brcmstb_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!
-- 
Florian