linux-kernel - Re: [PATCH v3 2/5] mfd: sec: Add support for S2MPS15 PMIC

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Message-id: <56319E36.1000700@samsung.com>
Date:	Thu, 29 Oct 2015 09:49:02 +0530
From:	Alim Akhtar <alim.akhtar@...sung.com>
To:	Lee Jones <lee.jones@...aro.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	k.kozlowski.k@...il.com, broonie@...nel.org,
	mturquette@...libre.com, linux-samsung-soc@...r.kernel.org,
	linux-clk@...r.kernel.org, rtc-linux@...glegroups.com,
	linux-kernel@...r.kernel.org,
	Thomas Abraham <thomas.ab@...sung.com>
Subject: Re: [PATCH v3 2/5] mfd: sec: Add support for S2MPS15 PMIC



On 10/28/2015 07:21 PM, Lee Jones wrote:
> On Wed, 28 Oct 2015, Krzysztof Kozlowski wrote:
>
>> W dniu 28.10.2015 o 17:46, Lee Jones pisze:
>>> On Wed, 28 Oct 2015, Krzysztof Kozlowski wrote:
>>>
>>>> On 26.10.2015 23:34, Lee Jones wrote:
>>>>> On Mon, 26 Oct 2015, Alim Akhtar wrote:
>>>>>
>>>>>> From: Thomas Abraham <thomas.ab@...sung.com>
>>>>>>
>>>>>> Add support for S2MPS15 PMIC which is similar to S2MPS11 PMIC. The S2MPS15
>>>>>> PMIC supports 27 LDO regulators, 10 buck regulators, RTC, three 32.768KHz
>>>>>> clock outputs and battery charger. This patch adds initial support for
>>>>>> LDO and buck regulators of S2MPS15 device.
>>>>>>
>>>>>> Signed-off-by: Thomas Abraham <thomas.ab@...sung.com>
>>>>>> Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
>>>>>> [Alim: Added s2mps15_devs like rtc and clk and related changes]
>>>>>> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
>>>>>> ---
>>>>>>   drivers/mfd/sec-core.c              |   31 +++++++
>>>>>>   drivers/mfd/sec-irq.c               |    8 ++
>>>>>>   include/linux/mfd/samsung/core.h    |    1 +
>>>>>>   include/linux/mfd/samsung/s2mps15.h |  158 +++++++++++++++++++++++++++++++++++
>>>>>>   4 files changed, 198 insertions(+)
>>>>>>   create mode 100644 include/linux/mfd/samsung/s2mps15.h
>>>>>
>>>>> I replied to the previous set and won't be reviewing this one until
>>>>> all of the open points are solved.
>>>>
>>>> The naming and compatibles used by the driver are confusing but how it
>>>> was at beginning. Beside the confusion, the names are correct:
>>>>
>>>> 1. Main mfd driver:
>>>>   - compatible: samsung,s2mps1*-pmic
>>>>   - driver name: sec_pmic
>>>>
>>>> 2. Regulator driver:
>>>>   - no compatible (because it always searches for "regulators" subnode of
>>>> its parent... that is the convention/legacy behaviour)
>>>>   - driver name: s2mps1*-pmic
>>>>
>>>> I hope that explains your concerns.
>>>
>>> It explains *why*, but doesn't ease my concerns in any way.
>>>
>>> Unfortunately I've only just realised the disparity we have between
>>> MFD and the Regulator subsystem, which is annoying because it's now
>>> almost impossible to rectify.
>>>
>>> We should have taken one of two views.  Either a) The MFD is the PMIC
>>> device which encompasses regulator control.  In which case the MFD
>>> and it's corresponding compatible string would be named *-pmic and the
>>> regulator driver would be called *-regulator. Or b) The MFD could be
>>> considered a normal MFD and be named after the model number, then the
>>> regulator 'could' be named *-pmic.
>>>
>>> However, with reference to b), how much other Power Management does
>>> the regulator driver do besides control regulators?  I suspect not
>>> much.  Therefore my preference would be for a).  My second choice
>>> would be a mixuture of the two where nothing gets named *-pmic.  The
>>> last option on my list would be the current situation where we seem to
>>> be calling both the MFD (PMIC) itself and the Regulator driver
>>> *-pmic, which is not good.
>>
>> Starting from the description of device-family. This is called "Power
>> Management IC" but it is rather a "Power Deliver/Distribute IC". There
>> isn't any logic inside except enable/disable/configure/set low power
>> mode for regulators.
>>
>> However in the same time the IC comes (always) with:
>>   - 32kHz clocks,
>>   - RTC,
>>   - backup battery charger (no driver for it),
>>   - reset for SoC,
>>   - shutdown on thermal alert (also no driver for this control).
>>
>> The solution a) seems fine to me. Make sense and it looks entirely
>> backward compatible - only driver names will be modified.
>
> Perfect solution from my PoV.
>
> Thanks Krzysztof.
>
Thanks Jones/Krzysztof as always.
Will update the patches.


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