Re: [PATCH V5 10/14] Documentation: DT: bindings: Add power domain info for NVIDIA PMC

[Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 03/02/16 15:48, Rob Herring wrote:
> On Wed, Feb 3, 2016 at 5:02 AM, Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> wrote:
>>
>> On 29/01/16 16:06, Rob Herring wrote:
>>> On Thu, Jan 28, 2016 at 04:33:48PM +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-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>>>> ---
>>>>  .../bindings/arm/tegra/nvidia,tegra20-pmc.txt      | 55 ++++++++++++++++++++++
>>>>  1 file changed, 55 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
>>>> index 53aa5496c5cf..3c77373aa826 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.
>>>> @@ -70,6 +72,10 @@ 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:
>>>> +- powergates : This node contains a hierarchy of power domain nodes, which
>>>> +           should match the powergates on the Tegra SoC.
>>>> +
>>>>  Example:
>>>>
>>>>  / SoC dts including file
>>>> @@ -115,3 +121,52 @@ pmc@7000f400 {
>>>>      };
>>>>      ...
>>>>  };
>>>> +
>>>> +
>>>> +== 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.
>>>
>>> Why not make this value be the power-domain cell for consumers and the
>>> pmc be the phandle.
>>
>> Is there anything wrong with using a label for the consumers? Seems
>> simpler, if you can just say ...
>>
>>         adma: adma@702e2000 {
>>                 ...
>>                 power-domains = <&pd_audio>;
>>                 ...
>>         };
> 
> Only that is a bit unusual. It would only really matter if we had some
> common parsing that we wanted to share. I'd look at other examples and
> try to align. If there's no clear pattern, then it is fine.

So I have been having a look at this and it appears to be mixed across
the various SoCs. It seems that those SoCs that define the generic PM
domains statically in the machine/soc code use a phandle plus a argument
to identify the power domain. However, for those that describe the
power-domain in the DT (listing clocks, resets, etc), they just use a
phandle to the power-domain itself (like I have above). It looks like if
you are describing the power domain in DT, then it is much simplier to
do this.

Given that I wish to keep the description of the power-domain in DT, it
is much easier to stick with the same conventions that the other SoCs
are using.

Cheers
Jon