Re: [PATCH] arm64: dts: qcom: sc7280.dtsi: prevent garbage on serial port

[Stephan Gerhold <stephan.gerhold@linaro.org>]

On Thu, Jun 26, 2025 at 03:23:30PM +0200, Casey Connolly wrote:
> During early boot phases there can be garbage characters on the serial
> RX port unless it is configured as pull-up. Add the pull-up bias and
> mark the rx/tx pinconfs as being necessary for all boot phases.
> 
> Signed-off-by: Casey Connolly <casey.connolly@linaro.org>
> ---
>  arch/arm64/boot/dts/qcom/sc7280.dtsi | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> index 64a2abd30100..60e4a311405a 100644
> --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> @@ -5742,13 +5742,16 @@ qup_uart4_rx: qup-uart4-rx-state {
>  
>  			qup_uart5_tx: qup-uart5-tx-state {
>  				pins = "gpio22";
>  				function = "qup05";
> +				bootph-all;

I'd add bias-disable here to have consistent state applied to both pins
and not just the RX one.

Thanks,
Stephan

>  			};
>  
>  			qup_uart5_rx: qup-uart5-rx-state {
>  				pins = "gpio23";
>  				function = "qup05";
> +				bootph-all;
> +				bias-pull-up;
>  			};
>  
>  			qup_uart6_cts: qup-uart6-cts-state {
>  				pins = "gpio24";
> -- 
> 2.50.0
>