Using PWM with nrf52840DK on pin 0.20

Question

I'm using nrf52840 DK and trying to get PWM working on pin 0.20. My code works fine when moving pin into eg. 1.15. What do I need to do configure eg. PIN 0.20 to be PWM enabled?

I've also disabled SPI blocks that were using those PINs.

 pwm_pump {
    compatible = "pwm-leds";
    pump_control: pwm_pump_0 {
        pwms = <&pwm0 0 PWM_USEC(1250) PWM_POLARITY_NORMAL>;
        status = "okay";
    };
    pwm-names = "pump";
    };

    pwm_light {
        compatible = "pwm-leds";
        light_control:light_0 {
            pwms = <&pwm1 1 PWM_USEC(1000) PWM_POLARITY_NORMAL>;
            status = "okay";
        };
        pwm-names = "light";
    };

&pwm0 {
    status = "okay";
    pinctrl-0 = <&pwm0_default_alt>;
    pinctrl-1 = <&pwm0_sleep_alt>;
    pinctrl-names = "default", "sleep";
};

&pwm1 {
    status = "okay";
    pinctrl-0 = <&pwm1_default_alt>;
    pinctrl-1 = <&pwm1_sleep_alt>;
    pinctrl-names = "default", "sleep";
};

&pinctrl {
    pwm0_default_alt: pwm0_default_alt {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 20)>;
        };
    };

    pwm0_sleep_alt: pwm0_sleep_alt {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 20)>;
            low-power-enable;
        };
    };

    pwm1_default_alt: pwm1_default_alt {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 19)>;
        };
    };

    pwm1_sleep_alt: pwm1_sleep_alt {
        group1 {
            psels = <NRF_PSEL(PWM_OUT0, 0, 19)>;
            low-power-enable;
        };
    };
};

SvenDufva · Accepted Answer

Let me answer my own question. Page 25 & 27 in nrf52840DK (or link https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nrf52840_dk%2FUG%2Fdk%2Fintro.html ) explains the reason. Pin 0.20 is used for driving external memory through QSPI and while they can be repurposed for other use, it requires some HW turning in DK.