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-rw-r--r--doc/device-tree-bindings/pinctrl/pinctrl-bindings.txt65
1 files changed, 59 insertions, 6 deletions
diff --git a/doc/device-tree-bindings/pinctrl/pinctrl-bindings.txt b/doc/device-tree-bindings/pinctrl/pinctrl-bindings.txt
index b73c96d24f..603796f169 100644
--- a/doc/device-tree-bindings/pinctrl/pinctrl-bindings.txt
+++ b/doc/device-tree-bindings/pinctrl/pinctrl-bindings.txt
@@ -119,7 +119,8 @@ For example:
The contents of each of those pin configuration child nodes is defined
entirely by the binding for the individual pin controller device. There
-exists no common standard for this content.
+exists no common standard for this content. The pinctrl framework only
+provides generic helper bindings that the pin controller driver can use.
The pin configuration nodes need not be direct children of the pin controller
device; they may be grandchildren, for example. Whether this is legal, and
@@ -156,6 +157,29 @@ state_2_node_a {
pins = "mfio29", "mfio30";
};
+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 provided with mux configuration settings
+in a pinmux group. A pinmux group consists of the pin identifier and mux
+settings represented as a single integer or an array of integers.
+
+The pinmux property accepts an array of pinmux groups, each of them describing
+a single pin multiplexing configuration.
+
+pincontroller {
+ state_0_node_a {
+ pinmux = <PINMUX_GROUP>, <PINMUX_GROUP>, ...;
+ };
+};
+
+Each individual pin controller driver bindings documentation shall specify
+how pin IDs and pin multiplexing configuration are defined and assembled
+together in a pinmux group.
+
== Generic pin configuration node content ==
Many data items that are represented in a pin configuration node are common
@@ -168,12 +192,15 @@ 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
@@ -184,17 +211,30 @@ drive-push-pull - drive actively high and low
drive-open-drain - drive with open drain
drive-open-source - drive with open source
drive-strength - sink or source at most X mA
-input-enable - enable input on pin (no effect on output)
-input-disable - disable input on pin (no effect on output)
+drive-strength-microamp - sink or source at most X uA
+input-enable - enable input on pin (no effect on output, such as
+ enabling an input buffer)
+input-disable - disable input on pin (no effect on output, such as
+ disabling an input buffer)
input-schmitt-enable - enable schmitt-trigger mode
input-schmitt-disable - disable schmitt-trigger mode
input-debounce - debounce mode with debound time X
power-source - select between different power supplies
low-power-enable - enable low power mode
low-power-disable - disable low power mode
+output-disable - disable output on a pin (such as disable an output
+ buffer)
+output-enable - enable output on a pin without actively driving it
+ (such as enabling an output buffer)
output-low - set the pin to output mode with low level
output-high - set the pin to output mode with high level
+sleep-hardware-state - indicate this is sleep related state which will be programmed
+ into the registers for the sleep state.
slew-rate - set the slew rate
+skew-delay - this affects the expected clock skew on input pins
+ and the delay before latching a value to an output
+ pin. Typically indicates how many double-inverters are
+ used to delay the signal.
For example:
@@ -216,6 +256,12 @@ 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.
@@ -224,11 +270,18 @@ 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 or an array of integers.
+
- 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.
- drive-strength takes as argument the target strength in mA.
+- drive-strength-microamp takes as argument the target strength in uA.
+
- input-debounce takes the debounce time in usec as argument
or 0 to disable debouncing