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SubjectRe: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains
Hi Arnd,

On 11/10/2014 05:06 PM, Arnd Bergmann wrote:
> On Monday 10 November 2014 16:59:16 Grygorii Strashko wrote:
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/power/ti,keystone-powerdomain.txt
>> @@ -0,0 +1,31 @@
>> +* TI Keystone 2 Generic PM Controller
>> +
>> +The TI Keystone 2 Generic PM Controller is responsible for Clock gating
>> +for each controlled IP module.
>> +
>> +Required properties:
>> +- compatible: Should be "ti,keystone-powerdomain"
>> +- #power-domain-cells: Should be 0, see below:
>> +
>> +The PM Controller node is a PM domain as documented in
>> +Documentation/devicetree/bindings/power/power_domain.txt.
>> +
>> +Example:
>> +
>> + pm_controller: pm-controller {
>> + compatible = "ti,keystone-powerdomain";
>> + #power-domain-cells = <0>;
>> + };
>> +
>> + netcp: netcp@2090000 {
>> + reg = <0x2620110 0x8>;
>> + reg-names = "efuse";
>> + ...
>> + #address-cells = <1>;
>> + #size-cells = <1>;
>> + ranges;
>> + power-domains = <&pm_controller>;
>> +
>> + clocks = <&clkpa>, <&clkcpgmac>, <&chipclk12>;
>> + dma-coherent;
>> + }
>
> I don't get it. What keystone specific about a "ti,keystone-powerdomain"
> device? It seems that the device has no registers whatsoever and the
> driver doesn't really do anything that relates to the platform.

That's true. but it was the only one acceptable way to enable
Generic clock manipulation PM callbacks for the DT-boot case.
After several unsuccessful attempts the idea to use GPD
was introduced by Kevin there:
https://lkml.org/lkml/2014/9/8/643

So, The Keystone 2 Generic PM Controller is just a proxy PM layer here between
device and Generic clock manipulation PM callbacks.
It fills per-device clock list when device is attached to GPD and
ensures that all clocks from that list enabled/disabled when device is
started/stopped.

Regards,
-grygorii


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