On Fri, 18 May 2018, Amelie DELAUNAY wrote:

On 05/17/2018 08:36 AM, Lee Jones wrote:

quoted

On Wed, 16 May 2018, Amelie DELAUNAY wrote:

quoted

On 05/16/2018 04:20 PM, Linus Walleij wrote:

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On Wed, May 9, 2018 at 9:56 AM, Amelie DELAUNAY [off-list ref] wrote:

quoted

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 [???]
Linaro Services Technical Lead
Linaro.org ? Open source software for ARM SoCs
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