linux-kernel - Re: [PATCH 5/6] mfd: devicetree: bindings: 88pm800: Add DT property for dual phase enable

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Date:	Mon, 13 Jul 2015 17:10:03 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Cc:	devicetree@...r.kernel.org, sameo@...ux.intel.com,
	linux-kernel@...r.kernel.org, robh+dt@...nel.org,
	lee.jones@...aro.org
Subject: Re: [PATCH 5/6] mfd: devicetree: bindings: 88pm800: Add DT property
 for dual phase enable

On 13.07.2015 16:50, Vaibhav Hiremath wrote:
> 
> 
> On Saturday 11 July 2015 12:46 PM, Krzysztof Kozlowski wrote:
>> W dniu 09.07.2015 o 20:47, Vaibhav Hiremath pisze:
>>> 88PM860 family of device supports dual phase mode on BUCK1 supply
>>> providing total 6A capacity.
>>> Note that by default they operate independently with 3A capacity.
>>>
>>> This patch adds the devicetree binding to enable this
>>> feature.
>>>
>>> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
>>> ---
>>>   Documentation/devicetree/bindings/mfd/88pm800.txt | 6 ++++++
>>>   1 file changed, 6 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/mfd/88pm800.txt
>>> b/Documentation/devicetree/bindings/mfd/88pm800.txt
>>> index ae1311c..c756b31 100644
>>> --- a/Documentation/devicetree/bindings/mfd/88pm800.txt
>>> +++ b/Documentation/devicetree/bindings/mfd/88pm800.txt
>>> @@ -15,6 +15,12 @@ Optional properties :
>>>         CLK32K3 - for 88pm800
>>>         CLK32K2 - for 88pm860
>>>
>>> +   (Applicable only to PXA910 family):
>>> +
>>> + - marvell,88pm860-buck1-dualphase-en    : If set, enable dual phase
>>> on BUCK1,
>>> +   providing 6A capacity.
>>> +   Without this both BUCK1A and BUCK1B operates independently with
>>> 3A capacity.
>>> +
>>
>> 1. How does this relates to regulator driver? The
>> drivers/regulator/88pm800.c defines constraints for regulator which may
>> be contradictory.
>>
>> 2. This looks like a job for regulator driver, not MFD. Then you could
>> use standard regulator bindings (setting maximum current to 6A would
>> change the regulator to different mode).
> 
> Make sense. and even better.
> 
> I believe you are referring to,
> 
> regulator-min-microamp = <3000000>;
> regulator-max-microamp = <6000000>;
> 
> And provide set_current_limit() callback, to set the dualphase.
> 
> Just to clarify more on this,
> 
> The DT property would look something like,
> 
> regulators {
>     compatible = "marvell,88pm80x-regulator";
> 
>     buck1a: BUCK1A {
>         regulator-compatible = "buck1";
>         regulator-min-microvolt = <600000>;
>         regulator-max-microvolt = <1800000>;
> 
>         regulator-min-microamp = <3000000>;
>         regulator-max-microamp = <6000000>;
> 
>         regulator-boot-on;
>         regulator-always-on;
>     };
> 
>     buck1b: BUCK1B {
>         regulator-compatible = "buck1b";
>         regulator-min-microvolt = <600000>;
>         regulator-max-microvolt = <1800000>;
> 
>         regulator-min-microamp = <3000000>;
>         regulator-max-microamp = <6000000>;
> 
>         regulator-boot-on;
>         regulator-always-on;
>     };
> };
> 
> 
> And for the platforms, where dual phase is not required,
> we can either choose not to set these properties or set it to
> 
> 
>         regulator-min-microamp = <3000000>;
>         regulator-max-microamp = <3000000>;

Yes, exactly. I only wonder if regulator core would support properly
such bindings - setting current limit for a voltage regulator. I didn't
tried this but it should work.

Best regards,
Krzysztof

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