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

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Message-ID: <20151028135149.GF4058@x1>
Date:	Wed, 28 Oct 2015 13:51:49 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	k.kozlowski.k@...il.com, Alim Akhtar <alim.akhtar@...sung.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 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.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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