Re: [PATCH v4] drm/exynos: prepare FIMD clocks

From: Inki Dae <inki.dae@samsung.com>
To: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: linux-samsung-soc@vger.kernel.org,
	"patches@linaro.org" <patches@linaro.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Tomasz Figa <tomasz.figa@gmail.com>,
	DRI mailing list <dri-devel@lists.freedesktop.org>,
	Kukjin Kim <kgene.kim@samsung.com>,
	myungjoo.ham@samsung.com, Vikas Sajjan <vikas.sajjan@linaro.org>,
	linaro-kernel@lists.linaro.org,
	"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: Re: [PATCH v4] drm/exynos: prepare FIMD clocks
Date: Mon, 22 Apr 2013 19:20:02 +0900	[thread overview]
Message-ID: <CAAQKjZOQr-NSgmwC3qGMqfQUu3QSgVsXfZkxwzpYE-onyVhOZw@mail.gmail.com> (raw)
In-Reply-To: <51750E43.1050602@samsung.com>


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2013/4/22 Sylwester Nawrocki <s.nawrocki@samsung.com>

> 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 ?
>
>
That's what I want~~ :)


> Thanks,
> Sylwester
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>

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