[PATCH v4] drm/exynos: prepare FIMD clocks
Rafael J. Wysocki
rjw at sisk.pl
Mon Apr 22 04:42:43 PDT 2013
On Monday, April 22, 2013 12:37:36 PM Tomasz Figa wrote:
> On Monday 22 of April 2013 12:17:39 Sylwester Nawrocki wrote:
> > On 04/22/2013 12:03 PM, Inki Dae wrote:
> > > > Also looks good to me. But what if power domain was disabled without
> > > > pm
> > > > runtime? In this case, you must enable the power domain at machine
> > > > code or
> > > > bootloader somewhere. This way would not only need some hard codes
> > > > to turn
> > > > the power domain on but also not manage power management fully. This
> > > > is same as only the use of pm runtime interface(needing some hard
> > > > codes without pm runtime) so I don't prefer to add
> > > > clk_enable/disable to fimd probe(). I quite tend to force only the
> > > > use of pm runtime as possible. So please add the hard codes to
> > > > machine code or bootloader like you did for power domain if you
> > > > want to use drm fimd without pm runtime.
> > >
> > > That's not how the runtime PM, clock subsystems work:
> > >
> > > 1) When CONFIG_PM_RUNTIME is disabled, all the used hardware must be
> > > kept
> > > powered on all the time.
> > >
> > > 2) Common Clock Framework will always gate all clocks that have zero
> > > enable_count. Note that CCF support for Exynos is already merged for
> > > 3.10 and it will be the only available clock support method for
> > > Exynos.
> > >
> > > AFAIK, drivers must work correctly in both cases, with
> > > CONFIG_PM_RUNTIME
> > > enabled and disabled.
> > >
> > > Then is the driver worked correctly if the power domain to this device was
> > > disabled at bootloader without CONFIG_PM_RUNTIME and with clk_enable()? I
> > > think, in this case, the device wouldn't be worked correctly because the
> > > power of the device remains off. So you must enable the power domain
> > > somewhere. What is the difference between these two cases?
> >
> > How about making the driver dependant on PM_RUNTIME and making it always
> > use pm_runtime_* API, regardless if the platform actually implements runtime
> > PM or not ? Is there any issue in using the Runtime PM core always, rather
> > than coding any workarounds in drivers when PM_RUNTIME is disabled ?
>
> I don't think this is a good idea. This would mean that any user that from
> some reasons don't want to use PM_RUNTIME, would not be able to use the driver
> anymore.
>
> Rafael, Kevin, do you have any opinion on this?
I agree.
Drivers should work for CONFIG_PM_RUNTIME unset too and static inline stubs for
all runtime PM helpers are available in that case.
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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