How do I configure an stm32mp157c GPIO pin to output?

[GeorgeR]

I have configured the pins for uart7 to communicate with our zwave chip.

in kernel-source/arch/arm/boot/dts/stm32mp157c-dk2.dts

&uart7{
        pinctrl-names = "default", "sleep";
        pinctrl-0 = <&uart7_pins_a>;
        pinctrl-1 = <&uart7_sleep_pins_a>;
        status = "okay";
 
        zwave {
                uart7-gpios = <&gpioi 5 GPIO_ACTIVE_LOW>,
                              <&gpioi 7 GPIO_ACTIVE_LOW>,
                              <&gpioc 7 GPIO_ACTIVE_LOW>;
        };
        /* USER CODE BEGIN uart7 */
        /* USER CODE END uart7 */
};

kernel-source/arch/arm/boot/dts/stm32mp15-pinctrl.dtsi :

        uart7_pins_a: uart7-0 {
                pins1 {
                        pinmux = <STM32_PINMUX('A', 15, AF13)>; /* UART7_TX */
                        bias-disable;
                        drive-push-pull;
                        slew-rate = <0>;
                };
                pins2 {
                        pinmux = <STM32_PINMUX('E', 7, AF7)>; /* UART7_RX */
                        bias-disable;
                };
        };
 
        uart7_sleep_pins_a: uart7-sleep-0 {
                pins {
                        pinmux = <STM32_PINMUX('A', 15, ANALOG)>, /* UART7_TX */
                                 <STM32_PINMUX('E', 7, ANALOG)>; /* UART7_RX */
                };
        };

I want to control the chip with three output GPIO pins (C7, I5, and I7).

When I bitbake this and load it on the board, the configuration does not change. For C

# 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)

gpiochip2 - 16 lines:
        line   0:      unnamed       unused   input  active-high
        line   1:      unnamed       kernel   input  active-high [used]
        line   2:      unnamed       kernel   input  active-high [used]
        line   3:      unnamed       unused   input  active-high
        line   4:      unnamed       kernel   input  active-high [used]
        line   5:      unnamed       kernel   input  active-high [used]
        line   6:      unnamed       unused   input  active-high
        line   7:      unnamed       unused   input  active-high
        line   8:      unnamed       kernel   input  active-high [used]
        line   9:      unnamed       kernel   input  active-high [used]
        line  10:      unnamed       kernel   input  active-high [used]
        line  11:      unnamed       kernel   input  active-high [used]
        line  12:      unnamed       kernel   input  active-high [used]
        line  13:      unnamed       unused   input  active-high
        line  14:      unnamed       unused   input  active-high
        line  15:      unnamed       unused   input  active-high

and I

gpiochip8 - 12 lines:
        line   0:      unnamed       unused   input  active-high
        line   1:      unnamed       unused   input  active-high
        line   2:      unnamed       unused   input  active-high
        line   3:      unnamed       kernel   input  active-high [used]
        line   4:      unnamed       unused   input  active-high
        line   5:      unnamed       kernel   input  active-high [used]
        line   6:      unnamed       kernel   input  active-high [used]
        line   7:      unnamed       kernel   input  active-high [used]
        line   8:      unnamed       kernel   input  active-high [used]
        line   9:      unnamed       unused   input  active-high
        line  10:      unnamed       unused   input  active-high
        line  11:      unnamed  "interrupt"   input  active-high [used]

Where and how can I change the GPIO pins?

Can I change them in the kernel-source/arch/arm/boot/dts/stm32mp157c-dk2.dts and/or in kernel-source/arch/arm/boot/dts/stm32mp15-pinctrl.dtsi ?

Thanks in advance,

George

[PatrickF]

Hi @GeorgeR​ 

I'm not expert, but you should probably need to declare a driver in your 'zwave' section (something like "compatible = ....").

Or use a dummy device (i.e. no driver)

https://wiki.st.com/stm32mpu/wiki/How_to_control_a_GPIO_in_kernel_space

Otherwise, without specific driver nor any DT, you could control any 'free' GPIO:

https://wiki.st.com/stm32mpu/wiki/How_to_control_a_GPIO_in_userspace

This method could be used from any code (e.g. C or python), see also https://community.st.com/s/question/0D53W00001UZllVSAT

Regards.

[GeorgeR]

Thank you @PatrickF​, I will check out the information.

Regards,

@GeorgeR​