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From: Lee Jones <lee.jones@linaro.org>
To: Amelie DELAUNAY <amelie.delaunay@st.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Rob Herring <robh@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Alexandre TORGUE <alexandre.torgue@st.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/5] dt-bindings: pinctrl: document the STMFX pinctrl bindings
Date: Fri, 18 May 2018 14:52:37 +0100	[thread overview]
Message-ID: <20180518135237.GQ5130@dell> (raw)
In-Reply-To: <28c374e6-b440-f785-b371-03fe15c8bc4b@st.com>

On Fri, 18 May 2018, Amelie DELAUNAY wrote:

> On 05/17/2018 08:36 AM, Lee Jones wrote:
> > On Wed, 16 May 2018, Amelie DELAUNAY wrote:
> > 
> >>
> >>
> >> On 05/16/2018 04:20 PM, Linus Walleij wrote:
> >>> On Wed, May 9, 2018 at 9:56 AM, Amelie DELAUNAY <amelie.delaunay@st.com> wrote:
> >>>
> >>>> Indeed, stmfx has other functions than GPIO. But, after comments done
> >>>> here: [1] and there: [2], it has been decided to move MFD parent/GPIO
> >>>> child drivers into a single PINCTRL/GPIO driver because of the following
> >>>> reasons:
> >>>> - Other stmfx functions (IDD measurement and TouchScreen controller) are
> >>>> not used on any of the boards using an stmfx and supported by Linux, so
> >>>> no way to test these functions, and no need to maintain them while they
> >>>> are not being used.
> >>>> - But, in the case a new board will use more than GPIO function on
> >>>> stmfx, the actual implementation allow to easily extract common init
> >>>> part of stmfx and put it in an MFD driver.
> >>>>
> >>>> So I could remove gpio sub-node and put its contents in stmfx node and
> >>>> keep single PINCTRL/GPIO driver for the time being.
> >>>> Please advise,
> >>>
> >>> I would normally advice to use the right modeling from the start, create
> >>> the MFD driver and spawn the devices from there. It is confusing
> >>> if the layout of the driver(s) doesn't really match the layout of the
> >>> hardware.
> >>>
> >>> I understand that it is a pain to write new MFD drivers to get your
> >>> things going and it would be "nice to get this working really quick
> >>> now" but in my experience it is better to do it right from the start.
> >>>
> >>
> >> Hi Linus,
> >>
> >> Thanks for your advice. I understand the point.
> >> So, the right modeling would be to:
> >> - create an MFD driver with the common init part of stmfx
> >> - remove all common init part of stmfx-pinctrl driver and keep only all
> >> gpio/pinctrl functions.
> >>
> >> I will not develop the other stmfx functions (IDD measurement driver and
> >> TouchScreen controller driver) because, as explained ealier, they are
> >> not used on any of the boards using an stmfx and supported by Linux, so
> >> no way to test these functions, and no need to maintain them while they
> >> are not being used.
> >>
> >> Lee, are you OK with that ?
> > 
> > I missed a lot of this conversation I think, but from what I've read,
> > it sounds fine.
> > 
> 
> I summarize the situation:
> - I still don't have an official datasheet for STMFX device which could 
> justify the use of an MFD driver;
> - the MFD driver will contain the STMFX chip initialization stuff such 
> as regmap initialization (regmap structure will be shared with the 
> child), chip initialization, global interrupt management;
> - there will be only one child (GPIO/PINCTRL node) for the time being.
> 
> So, is "MFD driver + GPIO/PINCTRL driver" the right modeling, and does 
> it still sound fine after this summary ? :)

It is starting to sound like there will only ever be one child device,
which starts to cross the line into "this is not an MFD" (M = Multi)
territory.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

  reply	other threads:[~2018-05-18 13:52 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-11  9:47 [PATCH 0/5] Introduce STMFX I2C GPIO expander Amelie Delaunay
2018-04-11  9:47 ` [PATCH 1/5] dt-bindings: pinctrl: document the STMFX pinctrl bindings Amelie Delaunay
2018-04-16 18:19   ` Rob Herring
2018-04-26 12:49     ` Linus Walleij
2018-05-09  7:56       ` Amelie DELAUNAY
2018-05-16 14:20         ` Linus Walleij
2018-05-16 15:01           ` Amelie DELAUNAY
2018-05-17  6:36             ` Lee Jones
2018-05-18  7:29               ` Amelie DELAUNAY
2018-05-18 13:52                 ` Lee Jones [this message]
2018-05-18 15:13                   ` Amelie DELAUNAY
2018-05-24  7:13                 ` Linus Walleij
2018-05-28 11:39                   ` Amelie DELAUNAY
2018-05-29  7:36                     ` Lee Jones
2018-05-09  7:31     ` Amelie DELAUNAY
2018-04-11  9:47 ` [PATCH 2/5] pinctrl: Add STMFX GPIO expander Pinctrl/GPIO driver Amelie Delaunay
2018-04-12  3:11   ` kbuild test robot
2018-04-26 12:48   ` Linus Walleij
2018-05-09  9:13     ` Amelie DELAUNAY
2018-04-11  9:47 ` [PATCH 3/5] ARM: dts: stm32: add STMFX pinctrl/gpio expander support on stm32746g-eval Amelie Delaunay
2018-04-11  9:47 ` [PATCH 4/5] ARM: dts: stm32: add orange and blue leds " Amelie Delaunay
2018-04-11  9:47 ` [PATCH 5/5] ARM: dts: stm32: add joystick support " Amelie Delaunay

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