linux-kernel - Re: [PATCH 1/11] ARM: tegra: add function to control the GPU rail clamp

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Message-ID: <20150108080338.GA27845@ulmo.nvidia.com>
Date:	Thu, 8 Jan 2015 09:03:40 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Vince Hsu <vinceh@...dia.com>
Cc:	Peter De Schrijver <pdeschrijver@...dia.com>,
	Lucas Stach <dev@...xeye.de>, swarren@...dotorg.org,
	gnurou@...il.com, bskeggs@...hat.com, martin.peres@...e.fr,
	seven@...rod-online.com, samuel.pitoiset@...il.com,
	nouveau@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/11] ARM: tegra: add function to control the GPU rail
 clamp

On Thu, Jan 08, 2015 at 12:25:18PM +0800, Vince Hsu wrote:
> 
> On 01/07/2015 10:48 PM, Thierry Reding wrote:
> >* PGP Signed by an unknown key
> >
> >On Wed, Jan 07, 2015 at 10:28:29PM +0800, Vince Hsu wrote:
> >>On 04:08:52PM Jan 07, Peter De Schrijver wrote:
> >>>On Wed, Jan 07, 2015 at 02:27:10PM +0100, Thierry Reding wrote:
> >>>
> >>>>>Yeah. I plan to have the information of all the clock client of the
> >>>>>partitions and
> >>>>>the memory clients be defined statically in c source, e.g. pmc-tegra124.c.
> >>>>>All modules can declare which domain they belong to in DT. One domain can
> >>>>>be really power gated only when no module is awake. Note the clock clients
> >>>>>of
> >>>>>one domain might not equal to the clocks of the module. The reset is not
> >>>>>either.
> >>>>>So I don't get the clock and reset from module. How do you think?
> >>>>This whole situation is quite messy. The above sequence basically means
> >>>>that drivers can't reset hardware modules because otherwise they might
> >>>>race with the power domain code. It also means that we can't powergate
> >>>The powerdomain framework won't call any powergating method as long as a
> >>>module in the domain is still active. So as long as drivers don't try to
> >>>reset the hw without having done a pm_runtime_get(), we shouldn't have such
> >>>a race?
> >>Agree. And as long as the driver has the correct reset procedure, that should
> >>be fine to occur between power ungating and gating sequences.
> >>
> >>>>modules on demand because they might be in the same power domain as one
> >>>>other module that's still busy.
> >>>>
> >>>The powerdomain framework keeps track of which modules are active (by hooking
> >>>into runtime pm) and won't try to shutdown a domain unless all modules are
> >>>inactive.
> >>Yeah. By the way, that means we should start supporting runtime pm for all
> >>the modules to use generic power domain.
> >Indeed, that'll be a prerequisite before we can merge power domain
> >support. I do have a couple of local patches that add very rudimentary
> >runtime PM for various drivers. For starters we could probably just do
> >the
> >
> >	pm_runtime_enable(...);
> >	pm_runtime_get_sync(...)
> >
> >in the ->probe() and
> >
> >	pm_runtime_put_sync(...);
> >	pm_runtime_disable(...);
> >
> >in the ->remove() callbacks for those drivers. That's by no means
> >optimal but should get us pretty close to what we do now and still
> >support the generic power domains.
> Cool. Could you send me the patches?

Here are two examples:

	https://github.com/thierryreding/linux/commit/36b5c34f68edb8135b9afb3e62c7ce9a527d6793
	https://github.com/thierryreding/linux/commit/6a6145d9e0fcbd4f9599552181fc02f4606b6a0e

Thierry

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