pinctrl: generic: move function to amlogic-am4 driver

pinctrl: generic: move function to amlogic-am4 driver

pinconf_generic_dt_node_to_map_pinmux() is not actually a generic
function, and really belongs in the amlogic-am4 driver. There are three
reasons why.

First, and least, of the reasons is that this function behaves
differently to the other dt_node_to_map functions in a way that is not
obvious from a first glance. This difference stems for the devicetree
properties that the function is intended for use with, and how they are
typically used. The other generic dt_node_to_map functions support
platforms where the pins, groups and functions are described statically
in the driver and require a function that will produce a mapping from dt
nodes to these pre-established descriptions. No other code in the driver
is require to be executed at runtime.
pinconf_generic_dt_node_to_map_pinmux() on the other hand is intended for
use with the pinmux property, where groups and functions are determined
entirely from the devicetree. As a result, there are no statically
defined groups and functions in the driver for this function to perform
a mapping to. Other drivers that use the pinmux property (e.g. the k1)
their dt_node_to_map function creates the groups and functions as the
devicetree is parsed. Instead of that,
pinconf_generic_dt_node_to_map_pinmux() requires that the devicetree is
parsed twice, once by it and once at probe, so that the driver
dynamically creates the groups and functions before the dt_node_to_map
callback is executed. I don't believe this double parsing requirement is
how developers would expect this to work and is not necessary given
there are drivers that do not have this behaviour.

Secondly and thirdly, the function bakes in some assumptions that only
really match the amlogic platform about how the devicetree is constructed.
These, to me, are problematic for something that claims to be generic.

The other dt_node_to_map implementations accept a being called for
either a node containing pin configuration properties or a node
containing child nodes that each contain the configuration properties.
IOW, they support the following two devicetree configurations:

| cfg {
| 	label: group {
| 		pinmux = <asjhdasjhlajskd>;
| 		config-item1;
| 	};
| };

| label: cfg {
| 	group1 {
| 		pinmux = <dsjhlfka>;
| 		config-item2;
| 	};
| 	group2 {
| 		pinmux = <lsdjhaf>;
| 		config-item1;
| 	};
| };

pinconf_generic_dt_node_to_map_pinmux() only supports the latter.

The other assumption about devicetree configuration that the function
makes is that the labeled node's parent is a "function node". The amlogic
driver uses these "function nodes" to create the functions at probe
time, and pinconf_generic_dt_node_to_map_pinmux() finds the parent of
the node it is operating on's name as part of the mapping. IOW, it
requires that the devicetree look like:

| pinctrl@bla {
|
| 	func-foo {
| 		label: group-default {
| 			pinmuxes = <lskdf>;
| 		};
| 	};
| };

and couldn't be used if the nodes containing the pinmux and
configuration properties are children of the pinctrl node itself:

| pinctrl@bla {
|
| 	label: group-default {
| 		pinmuxes = <lskdf>;
| 	};
| };

These final two reasons are mainly why I believe this is not suitable as
a generic function, and should be moved into the driver that is the sole
user and originator of the "generic" function.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>