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

[Geert Uytterhoeven]

Hi Lina,

On Mon, Aug 24, 2015 at 9:50 PM, Lina Iyer <lina.iyer at linaro.org> wrote:
> On Fri, Aug 21 2015 at 15:04 -0600, Kevin Hilman wrote:
>> Geert Uytterhoeven <geert at linux-m68k.org> writes:
>>> On Fri, Aug 14, 2015 at 7:19 PM, Kevin Hilman <khilman at kernel.org> wrote:
>>>> On Fri, Aug 14, 2015 at 12:24 AM, Geert Uytterhoeven
>>>> <geert at linux-m68k.org> wrote:
>>>>> On Fri, Aug 14, 2015 at 5:40 AM, Kevin Hilman <khilman at kernel.org>
>>>>> wrote:
>>>>>> Geert Uytterhoeven <geert at linux-m68k.org> writes:
>>>>>>> On Wed, Aug 12, 2015 at 9:50 PM, Kevin Hilman <khilman at 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?

No, Kevin and I are discussing about transparent buses that need power
management, not about CPU devices.

Cfr. commit 89d463ea106dba53 ("drivers: bus: Add Simple Power-Managed Bus
Driver").

Sorry for the confusion...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at 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