Re: [PATCH v2 1/3] dt-bindings: add binding for i.MX8MQ IOMUXC

[Shawn Guo <shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Wed, Feb 07, 2018 at 09:41:22AM -0200, Fabio Estevam wrote:
> [Adding Shawn on Cc]

Thanks Fabio.

> On Wed, Feb 7, 2018 at 9:11 AM, Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
> 
> > My opinion is that all that is generic about padctrl is a device driver
> > saying "Put my pins into a suitable mode". That is what padctrl is good
> > for and we are there for years now. I have always been happy with the
> > plain register values in the device tree. Before device tree we had
> > exactly these values in the board files and I never heard anyone
> > complaining about it. There were defines for the bits in the register
> > which you could use when you were unhappy with plain register values.
> >
> > It's really trivial to look in the reference manual to make up the
> > needed register values. It's also trivial to take a register value
> > and look into the reference manual what this value does. Every
> > translation layer, call it generic properties, just makes things more
> > complicated. Often enough our input is register value tables
> > from either our customers our from spreadsheets from FSL/NXP. Every
> > translation layer in the way just means we have to translate the already
> > existing register values into something hoping that this correctly
> > translates back into the register values.
> >
> > It's not that some board designer comes up with "I need a drive strength
> > of 150mA" and wants to put that value into the device tree. Instead they
> > start with the reference manual, see which values they can (must) adjust
> > and then adjust the values until they are happy. No one wants to ask
> > questions like "How do I have to manipulate that device tree to change
> > that particular bit?"
> >
> > As said, I am happy with plain register values in the device tree and
> > I consider everything else overengineered.
> > FSL/NXP Reference Manuals are freely available and of high quality so
> > everybody can understand the register values. There's nothing magic to
> > them. That might change slightly when the Manuals are not available, but
> > even then I think that not the device tree ABI is the right place to
> > add that missing documentation.
> 
> I agree 100% with Sascha.

I would vote for not going generic pinconf either, as the controversy
here starts from something, that indicates the generic stuff doesn't
work for i.MX.

Shawn
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