General Purpose Input/Output (GPIO)

The STMicroelectronics STM32MP15 CPU has twelve GPIO ports:

10 GPIO ports (named A to J) with 16 I/Os
1 GPIO port (named K) with 8 I/Os
1 secure GPIO port (named Z) with 8 I/Os

GPIO naming

STM32MP15 GPIO signals are named on the schematics and hardware reference manual in the form Pxn where:

P stands for "port"
x is the GPIO port
n is the GPIO number within the port

For instance, PA12 refers to GPIOA 12.

GPIOs on the ConnectCore MP15

On the ConnectCore MP15 system-on-module:
- Many of the STM32MP15 GPIOs are available on the system-on-module, multiplexed with other functions.
On the ConnectCore MP15 Development Kit:
- The GPIO connector allows direct access to the following STM32MP15 GPIOs:
  - GPIOF 15
- GPIOC 3 is connected to ULED
- GPIOA 13 is connected to User button and LED 1
- GPIOA 14 is connected to User button and LED 2

See Hardware reference manuals for information about GPIO pins and their multiplexed functionality.

GPIOs on the SOM and carrier board are used for many purposes, such as:

Power enable line for transceivers
Reset line for controllers
LCD backlight control
Interrupt line
User LED
User button

Kernel configuration

Support for STM32MP15 GPIOs is automatically provided through CONFIG_PINCTRL_STM32MP157, automatically enabled for this CPU.

Kernel driver

The driver for the STM32MP15 GPIO is located at:

File Description

File	Description
`drivers/pinctrl/stm32/pinctrl-stm32.c`	STM32MP15 Pinctrl driver to control GPIOs
`drivers/pinctrl/stm32/pinctrl-stm32mp157.c`	STM32MP157 Pinctrl driver

drivers/pinctrl/stm32/pinctrl-stm32.c

STM32MP15 Pinctrl driver to control GPIOs

drivers/pinctrl/stm32/pinctrl-stm32mp157.c

STM32MP157 Pinctrl driver

Device tree bindings and customization

The STM32MP15 GPIO device tree binding is documented at Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml.

One GPIO controller is defined for each STM32MP15 GPIO port in the common STM32MP15 device tree file:

STM32MP15 device tree

pinctrl: pin-controller@50002000 {
	#address-cells = <1>;
	#size-cells = <1>;
	compatible = "st,stm32mp157-pinctrl";
	ranges = <0 0x50002000 0xa400>;
	interrupt-parent = <&exti>;
	st,syscfg = <&exti 0x60 0xff>;
	hwlocks = <&hsem 0 1>;
	pins-are-numbered;

	gpioa: gpio@50002000 {
		gpio-controller;
		#gpio-cells = <2>;
		interrupt-controller;
		#interrupt-cells = <2>;
		reg = <0x0 0x400>;
		clocks = <&rcc GPIOA>;
		st,bank-name = "GPIOA";
		status = "disabled";
	};
...
	gpiok: gpio@5000c000 {
		gpio-controller;
		#gpio-cells = <2>;
		interrupt-controller;
		#interrupt-cells = <2>;
		reg = <0xa000 0x400>;
		clocks = <&rcc GPIOK>;
		st,bank-name = "GPIOK";
		status = "disabled";
	};
};
pinctrl_z: pin-controller-z@54004000 {
	#address-cells = <1>;
	#size-cells = <1>;
	compatible = "st,stm32mp157-z-pinctrl";
	ranges = <0 0x54004000 0x400>;
	pins-are-numbered;
	interrupt-parent = <&exti>;
	st,syscfg = <&exti 0x60 0xff>;
	hwlocks = <&hsem 0 1>;

	gpioz: gpio@54004000 {
		gpio-controller;
		#gpio-cells = <2>;
		interrupt-controller;
		#interrupt-cells = <2>;
		reg = <0 0x400>;
		clocks = <&scmi_clk CK_SCMI_GPIOZ>;
		st,bank-name = "GPIOZ";
		st,bank-ioport = <11>;
		status = "disabled";
	};
};

The ConnectCore MP15 device tree include file and the carrier board device tree files use the STM32MP15 GPIOs.

For example, on the ConnectCore MP15 Development Kit, Port G GPIO 0 is used to reset the PHY of Ethernet interface:

ConnectCore MP15 Development Kit device tree

&ethernet0 {
        status = "okay";
        pinctrl-0 = <&{pfm_slug}_ethernet0_rgmii_pins>;
        pinctrl-1 = <&{pfm_slug}_ethernet0_rgmii_sleep_pins>;
        pinctrl-names = "default", "sleep";
        phy-mode = "rgmii-id";
        max-speed = <1000>;
        phy-handle = <&phy0>;
        phy-supply = <&reg_3v3_eth_pwr>;

        mdio0 {
                #address-cells = <1>;
                #size-cells = <0>;
                compatible = "snps,dwmac-mdio";

                phy0: ethernet-phy@0 {
                        reg = <0>;
                        compatible = "ethernet-phy-id0141.0dd0"; /* PHY ID for Marvell 88E1512 */
                        reset-gpios = <&gpiog 0 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
                        reset-assert-us = <1000>;
                        reset-deassert-us = <2000>;
                };
        };
};

IOMUX configuration

For GPIOs that are managed by other drivers, you must define the port, GPIO number, and polarity.

ConnectCore MP15 device tree

&spi4 {
        pinctrl-names = "default", "sleep";
        pinctrl-0 = <&spi4_pins_b>;
        pinctrl-1 = <&spi4_sleep_pins_b>;
        cs-gpios = <&gpioe 11 GPIO_ACTIVE_HIGH>;
        status = "okay";
};

Using the GPIOs

The package libgpiod (added by packagegroup-dey-core) provides a set of tools (such as gpioset, gpioget, etc.) to control the GPIOs from user space.

You can still control the GPIOs from the sysfs, but this ABI is not recommended. See https://www.kernel.org/doc/html/latest/userspace-api/gpio/sysfs.html.

Detect GPIO ports

Use gpiodetect to list the GPIO ports detected by the kernel:

# gpiodetect
gpiochip0 [GPIOA] (16 lines)
gpiochip1 [GPIOB] (16 lines)
gpiochip2 [GPIOC] (16 lines)
gpiochip3 [GPIOD] (16 lines)
gpiochip4 [GPIOE] (16 lines)
gpiochip5 [GPIOF] (16 lines)
gpiochip6 [GPIOG] (16 lines)
gpiochip7 [GPIOH] (16 lines)
gpiochip8 [GPIOI] (12 lines)
gpiochip9 [GPIOZ] (8 lines)

where:

Ports GPIOA to GPIOZ are the STM32MP15 GPIO ports.

Information about a GPIO port

Use gpioinfo to list the lines of a given port:

# gpioinfo GPIOC
gpiochip2 - 16 lines:
line   0:        "PC0"       kernel   input  active-high [used]
        line   1:        "PC1"       kernel   input  active-high [used]
        line   2:        "PC2"       kernel   input  active-high [used]
        line   3:        "PC3"       unused  output  active-high
        line   4:        "PC4"       kernel   input  active-high [used]
        line   5:        "PC5"       kernel   input  active-high [used]
        line   6:        "PC6"       kernel   input  active-high [used]
        line   7:        "PC7"       unused   input  active-high
        line   8:        "PC8"       unused   input  active-high
        line   9:        "PC9" "regulators:regulator@2" output active-high [used]
        line  10:       "PC10" "regulators:regulator@1" output active-high [used]
        line  11:       "PC11"    "PCIe-EN"  output  active-high [used]
        line  12:       "PC12"       unused   input  active-high
        line  13:       "PC13"       unused   input  active-high
        line  14:       "PC14"       unused   input  active-high
        line  15:       "PC15"       unused   input  active-high

Set an output high/low

Use gpioset to set a STM32MP15 GPIO as output, such as GPIOC 3 (ULED). Use =1 to set it high, or =0 to set it low:

# gpioset GPIOC 3=1
# gpioset GPIOC 3=0

Read an input

Use gpioget to read the value of a STM32MP15 GPIO input, such as GPIOC 3:

# gpioget GPIOC 3
0

Use a GPIO as interrupt

Use gpiomon to wait for an event on a given GPIO, such as PortA GPIO14 (User 2 button):

# gpiomon --num-events 1 --rising-edge GPIOA 14

See the README of libgpiod for more information on these tools.

The STM32MP15 SoC has a limitation in the number of GPIOs that can be used as interrupt lines. The Extended Interrupt and Event Controller (EXTI) can only handle up to 16 GPIO lines working as interrupt (EXTI0..EXTI15). The multiplexers work as shown in the following figure:

This means that if pin 1 of a given port (for instance, PB1) has been selected to work as interrupt, pin 1 of any other GPIO port cannot simultaneously work as interrupt. You must keep this in mind when designing your hardware to avoid using the same GPIO numbers as interrupt lines of two or more peripherals.

On the ConnectCore MP15 GPIO, PA0 is already configured as an interrupt, so other GPIOs with index 0 must not be used as interrupts.

Sample application

An example application called apix-gpio-example is included in the dey-examples-digiapix recipe (part of dey-examples package) of the meta-digi layer. This application shows how to manage GPIO lines using the Digi APIx library on the ConnectCore MP15 platform.

By default, the Get Started with ConnectCore Cloud Services demo application seizes the user button. To use the example, stop the cccs-gs-demo with the following command:

# systemctl stop cccs-gs-demo

Go to GitHub to see the application instructions and source code.

See GPIO API for more information about the GPIO APIx.