[PATCH] ARM: dts: at91: sama7g5ek: enable pull-up for serial debug line

[PATCH] ARM: dts: at91: sama7g5ek: enable pull-up for serial debug line

[Eugen Hristev]

If the serial tx/rx are floating, it can happen that bogus characters
are detected on the line at boot time. This leads to U-boot accidentally
thinking someone pressed a key to stop autoboot, thus stopping booting process.
This can happen if the serial cable is not connected. There are hardware
pull-ups on the board connected to serial cable VBUS.
To solve this when the cable is not plugged, enable internal pull-ups as well
for the tx/rx lines.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
 arch/arm/dts/sama7g5ek.dts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/dts/sama7g5ek.dts b/arch/arm/dts/sama7g5ek.dts
index ff9c9eb45c..3a4fdd38a5 100644
--- a/arch/arm/dts/sama7g5ek.dts
+++ b/arch/arm/dts/sama7g5ek.dts
@@ -122,7 +122,7 @@
 	pinctrl_flx3_default: flx3_default {
 		pinmux = <PIN_PD16__FLEXCOM3_IO0>,
 			 <PIN_PD17__FLEXCOM3_IO1>;
-		bias-disable;
+		bias-pull-up;
 	};
 
 	pinctrl_sdmmc0_cmd_data_default: sdmmc0_cmd_data_default {
-- 
2.25.1

[PATCH] ARM: dts: at91: sama7g5ek: enable pull-up for serial debug line

[Eugen.Hristev at microchip.com]

On 28.01.2021 10:14, Eugen Hristev wrote:
> If the serial tx/rx are floating, it can happen that bogus characters
> are detected on the line at boot time. This leads to U-boot accidentally
> thinking someone pressed a key to stop autoboot, thus stopping booting process.
> This can happen if the serial cable is not connected. There are hardware
> pull-ups on the board connected to serial cable VBUS.
> To solve this when the cable is not plugged, enable internal pull-ups as well
> for the tx/rx lines.
> 
> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> ---
>   arch/arm/dts/sama7g5ek.dts | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/dts/sama7g5ek.dts b/arch/arm/dts/sama7g5ek.dts
> index ff9c9eb45c..3a4fdd38a5 100644
> --- a/arch/arm/dts/sama7g5ek.dts
> +++ b/arch/arm/dts/sama7g5ek.dts
> @@ -122,7 +122,7 @@
>   	pinctrl_flx3_default: flx3_default {
>   		pinmux = <PIN_PD16__FLEXCOM3_IO0>,
>   			 <PIN_PD17__FLEXCOM3_IO1>;
> -		bias-disable;
> +		bias-pull-up;
>   	};
>   
>   	pinctrl_sdmmc0_cmd_data_default: sdmmc0_cmd_data_default {
> 

Applied to u-boot-atmel/master