[Adding Shawn on Cc]

On Wed, Feb 7, 2018 at 9:11 AM, Sascha Hauer [off-list ref] 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 am also happy with the current plain register values in device tree.

Having two methods (plain register values on most of i.MX SoCs and the
new generic one for imx7ulp, imx8mq) is confusing for the end users.

I would prefer to use the plain register values in device tree for all
i.MX SoCs instead.

Thanks
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