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

[Geert Uytterhoeven <geert@linux-m68k.org>]

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? If yes, I wouldn't have needed simple-pm-bus.c.
What if a driver is bound later?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds