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

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Date:	Thu, 8 Jan 2015 12:25:18 +0800
From:	Vince Hsu <vinceh@...dia.com>
To:	Thierry Reding <thierry.reding@...il.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 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?

Thanks,
Vince

>
> Thierry
>
> * Unknown Key
> * 0x7F3EB3A1

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