linux-kernel - Re: [PATCH-v2 2/2] regulator: 88pm800: Add support for configuration of dual phase on BUCK1

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Message-ID: <55C2F8CC.1010308@linaro.org>
Date:	Thu, 06 Aug 2015 11:33:56 +0530
From:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
CC:	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, robh+dt@...nel.org,
	broonie@...nel.org, lee.jones@...aro.org
Subject: Re: [PATCH-v2 2/2] regulator: 88pm800: Add support for configuration
 of dual phase on BUCK1



On Thursday 06 August 2015 05:28 AM, Krzysztof Kozlowski wrote:
> On 05.08.2015 17:45, Vaibhav Hiremath wrote:
>>
>>
>> On Thursday 23 July 2015 10:21 AM, Krzysztof Kozlowski wrote:
>>> 2015-07-22 1:23 GMT+09:00 Vaibhav Hiremath <vaibhav.hiremath@...aro.org>:
>>>> 88PM860 device supports dual phase mode on BUCK1 output.
>>>> In normal usecase, BUCK1A and BUCK1B operates independently with 3A
>>>> capacity. And they both can work as a dual phase providing 6A capacity.
>>>>
>>>> This patch updates the regulator driver to read the respective
>>>> DT property and enable dual-phase mode on BUCK1.
>>>>
>>>> Note that, this is init time (one time) initialization.
>>>>
>>
>> Sorry for delayed response, was on bed rest almost for week.
>>
>>>> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
>>>> ---
>>>>    drivers/regulator/88pm800.c | 31 +++++++++++++++++++++++++++++++
>>>>    include/linux/mfd/88pm80x.h |  3 +++
>>>>    2 files changed, 34 insertions(+)
>>>
>>> Don't you need to update the constraints also? I think the BUCK1
>>> regulator has fixed constraint of 3 A:
>>>     PM800_BUCK(buck1, BUCK1, BUCK_ENA, 0, 3000000, buck1_volt_range,
>>> 0x55),
>>> and now it can handle 6 A.
>>>
>>
>> Actually, BUCK1A and BUCK1B both combined together provide 6A capacity.
>> And as discussed earlier, we need board change for this.
>>
>> I am quite not sure.
>
> AFAIU the regulator driver creates one BUCK1 regulator with constraints
> 3 A. However after your change the regulator will handle up to 6 A.
>
> This means that constraints set by driver are wrong.
>
> Additionally I can't find BUCK1A and BUCK1B regulators. Driver provides
> only BUCK1.
>

My patch does add BUCK1A and BUCK1B, please refer to the PATCH[4/5] of
earlier series, which is accepted.

https://patchwork.kernel.org/patch/6810461/


>>
>> Should I read the property and update the constraint runtime during
>> probe?
>
> Driver should provide real constraints. Find the proper way to do this.
>
> The pm800_regulator_info[] array is not const so you can change it in
> whatever way you want (although it should be const for existing driver
> because regulator core accepts const and passing it to driver_data is
> not necessary).
>


Probably that is the only way to handle this.

how about,

As you mentioned, pm800_regulator_info[] is not constant, so I can 
update the constraint before regulator_register() and also do not
register BUCK1B, if dual phase is enabled.

So in summary,

if (dual phase is enabled)
{
	Update constraint of BUCK1 to 6A
	and do not register BUCK1B
} else {
	register both BUCK1A and BUCK1B with default constraint of 3A.
}

Thanks,
Vaibhav
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