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Documentation: pinctrl: Add "pinmux" property 

Document "pinmux" property as part of generic pin controller
documentation.
Fix 2 minor typos in documentation while at there.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Jacopo Mondi 2017-04-06 12:35:55 +02:00 committed by Linus Walleij
parent 6bffa7e163
commit 8d5e7c5df0
1 changed files with 41 additions and 5 deletions
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46
Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
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@ -162,8 +162,8 @@ state_2_node_a {
pins = "mfio29", "mfio30";
};
Optionally an altenative binding can be used if more suitable depending on the
pin controller hardware. For hardaware where there is a large number of identical
Optionally an alternative binding can be used if more suitable depending on the
pin controller hardware. For hardware where there is a large number of identical
pin controller instances, naming each pin and function can easily become
unmaintainable. This is especially the case if the same controller is used for
different pins and functions depending on the SoC revision and packaging.
@ -198,6 +198,28 @@ registers, and must not be a virtual index of pin instances. The reason for
this is to avoid mapping of the index in the dts files and the pin controller
driver as it can change.
For hardware where pin multiplexing configurations have to be specified for
each single pin the number of required sub-nodes containing "pin" and
"function" properties can quickly escalate and become hard to write and
maintain.
For cases like this, the pin controller driver may use the pinmux helper
property, where the pin identifier is packed with mux configuration settings
in a single integer.
The pinmux property accepts an array of integers, each of them describing
a single pin multiplexing configuration.
pincontroller {
state_0_node_a {
pinmux = <PIN_ID_AND_MUX>, <PIN_ID_AND_MUX>, ...;
};
};
Each individual pin controller driver bindings documentation shall specify
how those values (pin IDs and pin multiplexing configuration) are defined and
assembled together.
== Generic pin configuration node content ==
Many data items that are represented in a pin configuration node are common
@ -210,12 +232,15 @@ structure of the DT nodes that contain these properties.
Supported generic properties are:
pins - the list of pins that properties in the node
apply to (either this or "group" has to be
apply to (either this, "group" or "pinmux" has to be
specified)
group - the group to apply the properties to, if the driver
supports configuration of whole groups rather than
individual pins (either this or "pins" has to be
specified)
individual pins (either this, "pins" or "pinmux" has
to be specified)
pinmux - the list of numeric pin ids and their mux settings
that properties in the node apply to (either this,
"pins" or "groups" have to be specified)
bias-disable - disable any pin bias
bias-high-impedance - high impedance mode ("third-state", "floating")
bias-bus-hold - latch weakly
@ -258,6 +283,12 @@ state_2_node_a {
bias-pull-up;
};
};
state_3_node_a {
mux {
pinmux = <GPIOx_PINm_MUXn>, <GPIOx_PINj_MUXk)>;
input-enable;
};
};
Some of the generic properties take arguments. For those that do, the
arguments are described below.
@ -266,6 +297,11 @@ arguments are described below.
binding for the hardware defines:
- Whether the entries are integers or strings, and their meaning.
- pinmux takes a list of pin IDs and mux settings as required argument. The
specific bindings for the hardware defines:
- How pin IDs and mux settings are defined and assembled together in a single
integer.
- bias-pull-up, -down and -pin-default take as optional argument on hardware
supporting it the pull strength in Ohm. bias-disable will disable the pull.