[PATCH] stm32mp1: add pull-up for gpio button PA13 and PA14

[Patrice CHOTARD]

Hi Patrick

On 7/9/21 9:53 AM, Patrick Delaunay wrote:
> When a push-button is released and PA13/PA14 are defined as input (high-Z)
> the LED should not be active as the circuit is open but a small current
> leak through PCB or push-button close the circuit and allows a small LED
> bias giving erroneous level voltage.
> 
> So it is recommended to activate an internal pull-up in order to clearly
> fix the voltage at PA13/PA14 when button is released and to wait
> a short delay before to read the GPIO value only when the pull-up is
> correctly configured.
> 
> Signed-off-by: Patrick Delaunay <patrick.delaunay at foss.st.com>
> ---
> 
>  arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi | 4 ++--
>  arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi | 4 ++--
>  board/st/stm32mp1/stm32mp1.c             | 2 ++
>  3 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi b/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi
> index 6787619290..d44da7566f 100644
> --- a/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi
> +++ b/arch/arm/dts/stm32mp157a-dk1-u-boot.dtsi
> @@ -18,8 +18,8 @@
>  		u-boot,error-led = "error";
>  		u-boot,mmc-env-partition = "ssbl";
>  		st,adc_usb_pd = <&adc1 18>, <&adc1 19>;
> -		st,fastboot-gpios = <&gpioa 13 GPIO_ACTIVE_LOW>;
> -		st,stm32prog-gpios = <&gpioa 14 GPIO_ACTIVE_LOW>;
> +		st,fastboot-gpios = <&gpioa 13 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
> +		st,stm32prog-gpios = <&gpioa 14 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
>  	};
>  
>  	firmware {
> diff --git a/arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi b/arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi
> index f3002e995b..3b94218b2f 100644
> --- a/arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi
> +++ b/arch/arm/dts/stm32mp157c-ed1-u-boot.dtsi
> @@ -18,8 +18,8 @@
>  		u-boot,boot-led = "heartbeat";
>  		u-boot,error-led = "error";
>  		u-boot,mmc-env-partition = "ssbl";
> -		st,fastboot-gpios = <&gpioa 13 GPIO_ACTIVE_LOW>;
> -		st,stm32prog-gpios = <&gpioa 14 GPIO_ACTIVE_LOW>;
> +		st,fastboot-gpios = <&gpioa 13 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
> +		st,stm32prog-gpios = <&gpioa 14 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
>  	};
>  
>  	firmware {
> diff --git a/board/st/stm32mp1/stm32mp1.c b/board/st/stm32mp1/stm32mp1.c
> index 18b8870269..e1796e7e31 100644
> --- a/board/st/stm32mp1/stm32mp1.c
> +++ b/board/st/stm32mp1/stm32mp1.c
> @@ -155,6 +155,7 @@ static void board_key_check(void)
>  					       &gpio, GPIOD_IS_IN)) {
>  			log_debug("could not find a /config/st,fastboot-gpios\n");
>  		} else {
> +			udelay(20);
>  			if (dm_gpio_get_value(&gpio)) {
>  				log_notice("Fastboot key pressed, ");
>  				boot_mode = BOOT_FASTBOOT;
> @@ -168,6 +169,7 @@ static void board_key_check(void)
>  					       &gpio, GPIOD_IS_IN)) {
>  			log_debug("could not find a /config/st,stm32prog-gpios\n");
>  		} else {
> +			udelay(20);
>  			if (dm_gpio_get_value(&gpio)) {
>  				log_notice("STM32Programmer key pressed, ");
>  				boot_mode = BOOT_STM32PROG;
> 

Reviewed-by: Patrice Chotard <patrice.chotard at foss.st.com>

Thanks
Patrice