Re: [PATCH 2/9] PM / Domains: Remove dev->driver check for runtime PM

[Lina Iyer <lina.iyer@linaro.org>]

On Fri, Aug 21 2015 at 15:04 -0600, Kevin Hilman wrote:
>Geert Uytterhoeven <geert@linux-m68k.org> writes:
>
>> Hi Kevin,
>>
>> On Fri, Aug 14, 2015 at 7:19 PM, Kevin Hilman <khilman@kernel.org> wrote:
>>> On Fri, Aug 14, 2015 at 12:24 AM, Geert Uytterhoeven
>>> <geert@linux-m68k.org> wrote:
>>>> On Fri, Aug 14, 2015 at 5:40 AM, Kevin Hilman <khilman@kernel.org> wrote:
>>>>> Geert Uytterhoeven <geert@linux-m68k.org> writes:
>>>>>> On Wed, Aug 12, 2015 at 9:50 PM, Kevin Hilman <khilman@kernel.org> wrote:
>>>>>>> This check might have made sense before PM domains, but with PM domains,
>>>>>>> it's entirely possible to have a simple device without a driver and the
>>>>>>> PM domain handles all the necesary PM, so I think this check
>>>>>>> could/should be removed.
>>>>>>>
>>>>>>> Thoughts?
>>>>>>
>>>>>> Simple devices without a driver aren't handled automatically.
>>>>>> At minimum, the driver should call pm_runtime_enable(), cfr.
>>>>>> drivers/bus/simple-pm-bus.c.
>>>>>
>>>>> That's correct, and in the proof-of-concept stuff I hacked up and in
>>>>> Lina's series, the CPU "devices" do indeed to this.  Without that, they
>>>>> wouldn't end up ever taking this codepath through genpd's
>>>>> runtime_suspend and power_off hooks.
>>>>>
>>>>> Also, I'm not sure if your comment was meant to be an objection to the
>>>>> patch?  or if you're OK with it.
>>>>
>>>> My comment was purely meant as a response to "it's entirely possible to have a
>>>> simple device without a driver and the PM domain handles all the necesary PM".
>>>
>>> Right, so if the PM domain does the pm_runtime_enable() for these
>>> "simple" devices without drivers, they can still exist without a
>>> driver, and the PM domain doing all the magic.
>>
>> Is it possible to let the PM Domain do the pm_runtime_enable() itself in
>> the absence of a driver?
>
>Well, I suppose it's possible, not sure it's recommended. :)
>
>> If yes, I wouldn't have needed simple-pm-bus.c.
>> What if a driver is bound later?
>
>Yeah, you're approach is better.
>
I am not sure I understand the approach? Initialize the CPU devices as
"simple-pm-bus" compatible?

Thanks,
Lina