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

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Date:   Wed, 25 Apr 2018 14:29:59 -0500
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <dmitry.torokhov@...il.com>,
        <jeffy.chen@...k-chips.com>, <enric.balletbo@...labora.com>,
        <josephl@...dia.com>, <opendmb@...il.com>, <rjw@...ysocki.net>
Subject: Re: Lack of suspend/resume/shutdown ordering between GPIO providers
 and consumers



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
>>>>>     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!
>>
> 
> 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