Zephyr: Blink-Led example doesn't build on Nucleo_L476RG, STM32F4_DISCOVERY, Nucleo_F302R8, Nucleo_F401RE

[giellamoswhard]

Describe the bug
I've tried to build the BlinkLed example with the boards o_L476RG, STM32F4_DISCOVERY, Nucleo_F302R8, Nucleo_F401RE but it doesn't build

error "Choose supported PWM driver"

To Reproduce
Steps to reproduce the behavior:

1. cd zephyrproject/zephyr/samples/basic/blink_led
2. west build -b nucleo_f401re -- -DBOARD_ROOT=/home/giellamo/projects/zephyrproject/zephyr/boards
3. ../src/main.c:28:2: error: #error "Choose supported PWM driver"
   #error "Choose supported PWM driver"
   ^~~
   ../src/main.c: In function 'main':
   ../src/main.c:46:31: error: 'PWM_DRIVER' undeclared (first use in this function); did you mean 'PWR_CR_VOS'?
   pwm_dev = device_get_binding(PWM_DRIVER);
   ^~~~
   PWR_CR_VOS

Expected behavior
It should build

Environment (please complete the following information):

• OS: .g. Linux, MacOS, Windows)
• Toolchain Zephyr SDK
• Commit 2.1.99

Additional context
The boards seems to miss the pwmleds in the dts

[erwango]

Boards supporting/enabling PWM should declare the following or equivalent:

    pwmleds {
        compatible = "pwm-leds";        
                red_pwm_led: red_pwm_led {
            pwms = <&{/soc/timers@40014000/pwm} 1 4>;
        };
    };
    aliases {
        ...
        pwm-led0 = &red_pwm_led;
        ...
    };

[sercantun]

Could you please explain what is the 1 and 4 arguments are used for ?

pwms = <&{/soc/timers@40014000/pwm} 1 4>;

[erwango]

@sercantun, information is available in dts/bindings/pwm/st,stm32-pwm.yaml:

pwm-cells:
  - channel
# period in terms of nanoseconds
  - period

1: Channel number
4: Period

Period of 4ns looks odd. This should be verified.

[erwango]

@giellamoswhard can you check #22277 answers your question ?

[giellamoswhard]

Yes. Thank you very much.

[erwango]

I'm reopening the point.
It will be closed automatically when #22277 gets merged

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