pinctrl: samsung: Allow grouping multiple pinmux/pinconf nodes

One of remaining limitations of current pinctrl-samsung driver was
the inability to parse multiple pinmux/pinconf group nodes grouped
inside a single device tree node. It made defining groups of pins for
single purpose, but with different parameters very inconvenient.

This patch implements Tegra-like support for grouping multiple pinctrl
groups inside one device tree node, by completely changing the way
pin groups and functions are parsed from device tree. The code creating
pinctrl maps from DT nodes has been borrowed from pinctrl-tegra, while
the initial creation of groups and functions has been completely
rewritten with following assumptions:
 - each group consists of just one pin and does not depend on data
   from device tree,
 - each function is represented by a device tree child node of the
   pin controller, which in turn can contain multiple child nodes
   for pins that need to have different configuration values.

Device Tree bindings are fully backwards compatible. New functionality
can be used by defining a new pinctrl group consisting of several child
nodes, as on following example:

	sd4_bus8: sd4-bus-width8 {
		part-1 {
			samsung,pins = "gpk0-3", "gpk0-4",
					"gpk0-5", "gpk0-6";
			samsung,pin-function = <3>;
			samsung,pin-pud = <3>;
			samsung,pin-drv = <3>;
		};
		part-2 {
			samsung,pins = "gpk1-3", "gpk1-4",
					"gpk1-5", "gpk1-6";
			samsung,pin-function = <4>;
			samsung,pin-pud = <4>;
			samsung,pin-drv = <3>;
		};
	};

Tested on Exynos4210-Trats board and a custom Exynos4212-based one.

Signed-off-by: Tomasz Figa <[email protected]>
Acked-by: Kyungmin Park <[email protected]>
Reviewed-by: Stephen Warren <[email protected]>
Cc: [email protected]
Cc: Rob Herring <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>

Documentation/devicetree/bindings/pinctrl/samsung-pinctrl.txt

@@ -44,7 +44,11 @@ Required Properties:
 - Pin mux/config groups as child nodes: The pin mux (selecting pin function
   mode) and pin config (pull up/down, driver strength) settings are represented
   as child nodes of the pin-controller node. There should be atleast one
-  child node and there is no limit on the count of these child nodes.
+  child node and there is no limit on the count of these child nodes. It is
+  also possible for a child node to consist of several further child nodes
+  to allow grouping multiple pinctrl groups into one. The format of second
+  level child nodes is exactly the same as for first level ones and is
+  described below.
 
   The child node should contain a list of pin(s) on which a particular pin
   function selection or pin configuration (or both) have to applied. This
@@ -249,6 +253,23 @@ Example 1: A pin-controller node with pin groups.
 			samsung,pin-pud = <3>;
 			samsung,pin-drv = <0>;
 		};
+
+		sd4_bus8: sd4-bus-width8 {
+			part-1 {
+				samsung,pins = "gpk0-3", "gpk0-4",
+						"gpk0-5", "gpk0-6";
+				samsung,pin-function = <3>;
+				samsung,pin-pud = <3>;
+				samsung,pin-drv = <3>;
+			};
+			part-2 {
+				samsung,pins = "gpk1-3", "gpk1-4",
+						"gpk1-5", "gpk1-6";
+				samsung,pin-function = <4>;
+				samsung,pin-pud = <4>;
+				samsung,pin-drv = <3>;
+			};
+		};
 	};
 
 Example 2: A pin-controller node with external wakeup interrupt controller node.