linux-kernel - Re: [PATCH V4 12/16] Documentation: DT: bindings: Add power domain info for NVIDIA PMC

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Date:	Mon, 7 Dec 2015 09:56:55 +0000
From:	Jon Hunter <jonathanh@...dia.com>
To:	Rob Herring <robh@...nel.org>
CC:	Philipp Zabel <p.zabel@...gutronix.de>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Rafael Wysocki <rjw@...ysocki.net>,
	Kevin Hilman <khilman@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Vince Hsu <vinceh@...dia.com>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<linux-pm@...r.kernel.org>
Subject: Re: [PATCH V4 12/16] Documentation: DT: bindings: Add power domain
 info for NVIDIA PMC


On 06/12/15 00:37, Rob Herring wrote:
> On Fri, Dec 04, 2015 at 02:57:13PM +0000, Jon Hunter wrote:
>> Add power-domain binding documentation for the NVIDIA PMC driver in
>> order to support generic power-domains.
>>
>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>>
>> ---
>>
>> Please note that I have been debating whether I add this
>> "nvidia,powergate-clock-disable" property or just leave the clocks
>> disabled by default. Some downstream kernels leave the clocks enabled
>> for the audio power-domain because the clocks required for powering up
>> the power-domain are needed by all modules within the power-domain.
>> However are the same time there are other power-domains that may need
>> to be on, but not always clocked and so having the ability to specify if
>> the clocks should be disabled seems useful. However, I can also remove
>> this and just have the appropriate devices turn on the clocks as well.
> 
> Seems like that is just a failure of drivers to control all the clocks 
> they need IMO.

Right and that was why I was on the fence. However, I could see that
some domains may always need a bus clock on and so it did not seem
complete absurd. If the consensus is to drop it, I will.

>> ---
>>  .../bindings/arm/tegra/nvidia,tegra20-pmc.txt      | 61 ++++++++++++++++++++++
>>  1 file changed, 61 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
>> index 838e1a69ec0a..8e4641db51a9 100644
>> --- a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
>> +++ b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
>> @@ -1,5 +1,7 @@
>>  NVIDIA Tegra Power Management Controller (PMC)
>>  
>> +== Power Management Controller Node ==
>> +
>>  The PMC block interacts with an external Power Management Unit. The PMC
>>  mostly controls the entry and exit of the system from different sleep
>>  modes. It provides power-gating controllers for SoC and CPU power-islands.
>> @@ -69,6 +71,10 @@ Optional properties for hardware-triggered thermal reset (inside 'i2c-thermtrip'
>>                       Defaults to 0. Valid values are described in section 12.5.2
>>                       "Pinmux Support" of the Tegra4 Technical Reference Manual.
>>  
>> +Optional nodes:
>> +- pm-domains : This node contains a hierarchy of PM domain nodes, which should
>> +	       match the power-domains on the Tegra SoC.
>> +
>>  Example:
>>  
>>  / SoC dts including file
>> @@ -114,3 +120,58 @@ pmc@...0f400 {
>>  	};
>>  	...
>>  };
>> +
>> +
>> +== PM Domain Nodes ==
>> +
>> +Each of the PM domain nodes represents a power-domain on the Tegra SoC
>> +that can be power-gated by the PMC and should be named appropriately.
>> +
>> +Required properties:
>> +  - clocks: Must contain an entry for each clock required by the PMC for
>> +    controlling a power-gate. See ../clocks/clock-bindings.txt for details.
>> +  - resets: Must contain an entry for each reset required by the PMC for
>> +    controlling a power-gate. See ../reset/reset.txt for details.
>> +  - nvidia,powergate: Integer cell that contains an identifier for the PMC
>> +    power-gate that is associated with the power-domain. Please refer to
>> +    the Tegra TRM for more details.
> 
> "reg" does not work here?

Not really. This value is used to program a register to power-up/down
the particular power-domain you are interested in.

Cheers
Jon
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