Pinctrl and Pinmux

struct pinconf_param

pin config parameters

Definition

struct pinconf_param {
  const char * const property;
  unsigned int param;
  u32 default_value;
};

Members

property
Property name in DT nodes
param
ID for this config parameter
default_value
default value for this config parameter used in case no value is specified in DT nodes
struct pinctrl_ops

pin control operations, to be implemented by pin controller drivers.

Definition

struct pinctrl_ops {
  int (*get_pins_count)(struct udevice *dev);
  const char *(*get_pin_name)(struct udevice *dev, unsigned selector);
  int (*get_groups_count)(struct udevice *dev);
  const char *(*get_group_name)(struct udevice *dev, unsigned selector);
  int (*get_functions_count)(struct udevice *dev);
  const char *(*get_function_name)(struct udevice *dev, unsigned selector);
  int (*pinmux_set)(struct udevice *dev, unsigned pin_selector, unsigned func_selector);
  int (*pinmux_group_set)(struct udevice *dev, unsigned group_selector, unsigned func_selector);
  int (*pinmux_property_set)(struct udevice *dev, u32 pinmux_group);
  unsigned int pinconf_num_params;
  const struct pinconf_param *pinconf_params;
  int (*pinconf_set)(struct udevice *dev, unsigned pin_selector, unsigned param, unsigned argument);
  int (*pinconf_group_set)(struct udevice *dev, unsigned group_selector, unsigned param, unsigned argument);
  int (*set_state)(struct udevice *dev, struct udevice *config);
  int (*set_state_simple)(struct udevice *dev, struct udevice *periph);
  int (*request)(struct udevice *dev, int func, int flags);
  int (*get_periph_id)(struct udevice *dev, struct udevice *periph);
  int (*get_gpio_mux)(struct udevice *dev, int banknum, int index);
  int (*get_pin_muxing)(struct udevice *dev, unsigned int selector, char *buf, int size);
  int (*gpio_request_enable)(struct udevice *dev, unsigned int selector);
  int (*gpio_disable_free)(struct udevice *dev, unsigned int selector);
};

Members

get_pins_count

Get the number of selectable pins

dev: Pinctrl device to use

This function is necessary to parse the “pins” property in DTS.

Return:
number of selectable named pins available in this driver
get_pin_name

Get the name of a pin

dev: Pinctrl device of the pin

selector: The pin selector

This function is called by the core to figure out which pin it will do operations to. This function is necessary to parse the “pins” property in DTS.

Return: const pointer to the name of the pin

get_groups_count

Get the number of selectable groups

dev: Pinctrl device to use

This function is necessary to parse the “groups” property in DTS.

Return:
number of selectable named groups available in the driver
get_group_name

Get the name of a group

dev: Pinctrl device of the group

selector: The group selector

This function is called by the core to figure out which group it will do operations to. This function is necessary to parse the “groups” property in DTS.

Return: Pointer to the name of the group

get_functions_count

Get the number of selectable functions

dev: Pinctrl device to use

This function is necessary for pin-muxing.

Return:
number of selectable named functions available in this driver
get_function_name

Get the name of a function

dev: Pinmux device of the function

selector: The function selector

This function is called by the core to figure out which mux setting it will map a certain device to. This function is necessary for pin-muxing.

Return:
Pointer to the function name of the muxing selector
pinmux_set

Mux a pin to a function

dev: Pinctrl device to use

pin_selector: The pin selector

func_selector: The func selector

On simple controllers one of pin_selector or func_selector may be ignored. This function is necessary for pin-muxing against a single pin.

Return: 0 if OK, or negative error code on failure

pinmux_group_set

Mux a group of pins to a function

dev: Pinctrl device to use

group_selector: The group selector

func_selector: The func selector

On simple controllers one of group_selector or func_selector may be ignored. This function is necessary for pin-muxing against a group of pins.

Return: 0 if OK, or negative error code on failure

pinmux_property_set

Enable a pinmux group

dev: Pinctrl device to use

pinmux_group: A u32 representing the pin identifier and mux
settings. The exact format of a pinmux group is left up to the driver.

Mux a single pin to a single function based on a driver-specific pinmux group. This function is necessary for parsing the “pinmux” property in DTS, and for pin-muxing against a pinmux group.

Return:
Pin selector for the muxed pin if OK, or negative error code on failure
pinconf_num_params
Number of driver-specific parameters to be parsed from device trees. This member is necessary for pin configuration.
pinconf_params
List of driver-specific parameters to be parsed from the device tree. This member is necessary for pin configuration.
pinconf_set

Configure an individual pin with a parameter

dev: Pinctrl device to use

pin_selector: The pin selector

param: An enum pin_config_param from pinconf_params

argument: The argument to this param from the device tree, or
pinconf_params.default_value

This function is necessary for pin configuration against a single pin.

Return: 0 if OK, or negative error code on failure

pinconf_group_set

Configure all pins in a group with a parameter

dev: Pinctrl device to use

pin_selector: The group selector

param: A enum pin_config_param from
pinconf_params
argument: The argument to this param from the device tree, or
pinconf_params.default_value

This function is necessary for pin configuration against a group of pins.

Return: 0 if OK, or negative error code on failure

set_state

Configure a pinctrl device

dev: Pinctrl device to use

config: Pseudo device pointing a config node

This function is required to be implemented by all pinctrl drivers. Drivers may set this member to pinctrl_generic_set_state(), which will call other functions in struct pinctrl_ops to parse config.

Return: 0 if OK, or negative error code on failure

set_state_simple

Configure a pinctrl device

dev: Pinctrl device to use

config: Pseudo-device pointing a config node

This function is usually a simpler version of set_state(). Only the first pinctrl device on the system is supported by this function.

Return: 0 if OK, or negative error code on failure

request

Request a particular pinctrl function

dev: Device to adjust (UCLASS_PINCTRL)

func: Function number (driver-specific)

This activates the selected function.

Return: 0 if OK, or negative error code on failure

get_periph_id

Get the peripheral ID for a device

dev: Pinctrl device to use for decoding

periph: Device to check

This generally looks at the peripheral’s device tree node to work out the peripheral ID. The return value is normally interpreted as enum periph_id. so long as this is defined by the platform (which it should be).

Return:
Peripheral ID of periph, or -ENOENT on error
get_gpio_mux

Get the mux value for a particular GPIO

dev: Pinctrl device to use

banknum: GPIO bank number

index: GPIO index within the bank

This allows the raw mux value for a GPIO to be obtained. It is useful for displaying the function being used by that GPIO, such as with the ‘gpio’ command. This function is internal to the GPIO subsystem and should not be used by generic code. Typically it is used by a GPIO driver with knowledge of the SoC pinctrl setup.

Return:
Mux value (SoC-specific, e.g. 0 for input, 1 for output)
get_pin_muxing

Show pin muxing

dev: Pinctrl device to use

selector: Pin selector

buf: Buffer to fill with pin muxing description

size: Size of buf

This allows to display the muxing of a given pin. It’s useful for debug purposes to know if a pin is configured as GPIO or as an alternate function and which one. Typically it is used by a PINCTRL driver with knowledge of the SoC pinctrl setup.

Return: 0 if OK, or negative error code on failure

gpio_request_enable

Request and enable GPIO on a certain pin.

dev: Pinctrl device to use

selector: Pin selector

Implement this only if you can mux every pin individually as GPIO. The affected GPIO range is passed along with an offset(pin number) into that specific GPIO range - function selectors and pin groups are orthogonal to this, the core will however make sure the pins do not collide.

Return:
0 if OK, or negative error code on failure
gpio_disable_free

Free up GPIO muxing on a certain pin.

dev: Pinctrl device to use

selector: Pin selector

This function is the reverse of gpio_request_enable.

Return: 0 if OK, or negative error code on failure

Description

set_state() is the only mandatory operation. You can implement your pinctrl driver with its own set_state. In this case, the other callbacks are not required. Otherwise, generic pinctrl framework is also available; use pinctrl_generic_set_state for set_state, and implement other operations depending on your necessity.

enum pin_config_param

Generic pin configuration parameters

Constants

PIN_CONFIG_BIAS_BUS_HOLD
The pin will be set to weakly latch so that it weakly drives the last value on a tristate bus, also known as a “bus holder”, “bus keeper” or “repeater”. This allows another device on the bus to change the value by driving the bus high or low and switching to tristate. The argument is ignored.
PIN_CONFIG_BIAS_DISABLE
Disable any pin bias on the pin, a transition from say pull-up to pull-down implies that you disable pull-up in the process, this setting disables all biasing.
PIN_CONFIG_BIAS_HIGH_IMPEDANCE
The pin will be set to a high impedance mode, also know as “third-state” (tristate) or “high-Z” or “floating”. On output pins this effectively disconnects the pin, which is useful if for example some other pin is going to drive the signal connected to it for a while. Pins used for input are usually always high impedance.
PIN_CONFIG_BIAS_PULL_DOWN
The pin will be pulled down (usually with high impedance to GROUND). If the argument is != 0 pull-down is enabled, if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
PIN_CONFIG_BIAS_PULL_PIN_DEFAULT
The pin will be pulled up or down based on embedded knowledge of the controller hardware, like current mux function. The pull direction and possibly strength too will normally be decided completely inside the hardware block and not be readable from the kernel side. If the argument is != 0 pull up/down is enabled, if it is 0, the configuration is ignored. The proper way to disable it is to use PIN_CONFIG_BIAS_DISABLE.
PIN_CONFIG_BIAS_PULL_UP
The pin will be pulled up (usually with high impedance to VDD). If the argument is != 0 pull-up is enabled, if it is 0, pull-up is total, i.e. the pin is connected to VDD.
PIN_CONFIG_DRIVE_OPEN_DRAIN
The pin will be driven with open drain (open collector) which means it is usually wired with other output ports which are then pulled up with an external resistor. Setting this config will enable open drain mode, the argument is ignored.
PIN_CONFIG_DRIVE_OPEN_SOURCE
The pin will be driven with open source (open emitter). Setting this config will enable open source mode, the argument is ignored.
PIN_CONFIG_DRIVE_PUSH_PULL
The pin will be driven actively high and low, this is the most typical case and is typically achieved with two active transistors on the output. Setting this config will enable push-pull mode, the argument is ignored.
PIN_CONFIG_DRIVE_STRENGTH
The pin will sink or source at most the current passed as argument. The argument is in mA.
PIN_CONFIG_DRIVE_STRENGTH_UA
The pin will sink or source at most the current passed as argument. The argument is in uA.
PIN_CONFIG_INPUT_DEBOUNCE
This will configure the pin to debounce mode, which means it will wait for signals to settle when reading inputs. The argument gives the debounce time in usecs. Setting the argument to zero turns debouncing off.
PIN_CONFIG_INPUT_ENABLE
Enable the pin’s input. Note that this does not affect the pin’s ability to drive output. 1 enables input, 0 disables input.
PIN_CONFIG_INPUT_SCHMITT
This will configure an input pin to run in schmitt-trigger mode. If the schmitt-trigger has adjustable hysteresis, the threshold value is given on a custom format as argument when setting pins to this mode.
PIN_CONFIG_INPUT_SCHMITT_ENABLE
Control schmitt-trigger mode on the pin. If the argument != 0, schmitt-trigger mode is enabled. If it’s 0, schmitt-trigger mode is disabled.
PIN_CONFIG_LOW_POWER_MODE
This will configure the pin for low power operation, if several modes of operation are supported these can be passed in the argument on a custom form, else just use argument 1 to indicate low power mode, argument 0 turns low power mode off.
PIN_CONFIG_OUTPUT_ENABLE
This will enable the pin’s output mode without driving a value there. For most platforms this reduces to enable the output buffers and then let the pin controller current configuration (eg. the currently selected mux function) drive values on the line. Use argument 1 to enable output mode, argument 0 to disable it.
PIN_CONFIG_OUTPUT
This will configure the pin as an output and drive a value on the line. Use argument 1 to indicate high level, argument 0 to indicate low level. (Please see Documentation/driver-api/pinctl.rst, section “GPIO mode pitfalls” for a discussion around this parameter.)
PIN_CONFIG_POWER_SOURCE
If the pin can select between different power supplies, the argument to this parameter (on a custom format) tells the driver which alternative power source to use.
PIN_CONFIG_SLEEP_HARDWARE_STATE
Indicate this is sleep related state.
PIN_CONFIG_SLEW_RATE
If the pin can select slew rate, the argument to this parameter (on a custom format) tells the driver which alternative slew rate to use.
PIN_CONFIG_SKEW_DELAY
If the pin has programmable skew rate (on inputs) or latch delay (on outputs) this parameter (in a custom format) specifies the clock skew or latch delay. It typically controls how many double inverters are put in front of the line.
PIN_CONFIG_END
This is the last enumerator for pin configurations, if you need to pass in custom configurations to the pin controller, use PIN_CONFIG_END+1 as the base offset.
PIN_CONFIG_MAX
This is the maximum configuration value that can be presented using the packed format.
int pinctrl_generic_set_state(struct udevice *pctldev, struct udevice *config)

Generic set_state operation

Parameters

struct udevice *pctldev
Pinctrl device to use
struct udevice *config
Config device (pseudo device), pointing a config node in DTS

Description

Parse the DT node of config and its children and handle generic properties such as “pins”, “groups”, “functions”, and pin configuration parameters.

Return

0 on success, or negative error code on failure

int pinctrl_select_state(struct udevice *dev, const char *statename)

Set a device to a given state

Parameters

struct udevice *dev
Peripheral device
const char *statename
State name, like “default”

Return

0 on success, or negative error code on failure

int pinctrl_request(struct udevice *dev, int func, int flags)

Request a particular pinctrl function

Parameters

struct udevice *dev
Pinctrl device to use
int func
Function number (driver-specific)
int flags
Flags (driver-specific)

Return

0 if OK, or negative error code on failure

int pinctrl_request_noflags(struct udevice *dev, int func)

Request a particular pinctrl function

Parameters

struct udevice *dev
Pinctrl device to use
int func
Function number (driver-specific)

Description

This is similar to pinctrl_request() but uses 0 for flags.

Return

0 if OK, or negative error code on failure

int pinctrl_get_periph_id(struct udevice *dev, struct udevice *periph)

Get the peripheral ID for a device

Parameters

struct udevice *dev
Pinctrl device to use for decoding
struct udevice *periph
Device to check

Description

This generally looks at the peripheral’s device tree node to work out the peripheral ID. The return value is normally interpreted as enum periph_id. so long as this is defined by the platform (which it should be).

Return

Peripheral ID of periph, or -ENOENT on error

int pinctrl_get_gpio_mux(struct udevice *dev, int banknum, int index)

get the mux value for a particular GPIO

Parameters

struct udevice *dev
Pinctrl device to use
int banknum
GPIO bank number
int index
GPIO index within the bank

Description

This allows the raw mux value for a GPIO to be obtained. It is useful for displaying the function being used by that GPIO, such as with the ‘gpio’ command. This function is internal to the GPIO subsystem and should not be used by generic code. Typically it is used by a GPIO driver with knowledge of the SoC pinctrl setup.

Return

Mux value (SoC-specific, e.g. 0 for input, 1 for output)

int pinctrl_get_pin_muxing(struct udevice *dev, int selector, char *buf, int size)

Returns the muxing description

Parameters

struct udevice *dev
Pinctrl device to use
int selector
Pin index within pin-controller
char *buf
Pin’s muxing description
int size
Pin’s muxing description length

Description

This allows to display the muxing description of the given pin for debug purpose

Return

0 if OK, or negative error code on failure

int pinctrl_get_pins_count(struct udevice *dev)

Display pin-controller pins number

Parameters

struct udevice *dev
Pinctrl device to use

Description

This allows to know the number of pins owned by a given pin-controller

Return

Number of pins if OK, or -ENOSYS when not supported

int pinctrl_get_pin_name(struct udevice *dev, int selector, char *buf, int size)

Returns the pin’s name

Parameters

struct udevice *dev
Pinctrl device to use
int selector
Pin index within pin-controller
char *buf
Buffer to fill with the name of the pin
int size
Size of buf

Description

This allows to display the pin’s name for debug purpose

Return

0 if OK, or negative error code on failure

int pinctrl_gpio_request(struct udevice *dev, unsigned offset)

Request a single pin to be used as GPIO

Parameters

struct udevice *dev
GPIO peripheral device
unsigned offset
GPIO pin offset from the GPIO controller

Return

0 on success, or negative error code on failure

int pinctrl_gpio_free(struct udevice *dev, unsigned offset)

Free a single pin used as GPIO

Parameters

struct udevice *dev
GPIO peripheral device
unsigned offset
GPIO pin offset from the GPIO controller

Return

0 on success, or negative error code on failure