linux-kernel - Re: [V4 1/2] arch: arm64: dts: qcom: sc7280-idp: Configure cts pinctrl to bias-bus-hold

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Message-ID: <Yl9xoYo8z7z4gSTT@builder.lan>
Date:   Tue, 19 Apr 2022 21:36:17 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
Cc:     agross@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_msavaliy@...cinc.com, dianders@...omium.org
Subject: Re: [V4 1/2] arch: arm64: dts: qcom: sc7280-idp: Configure cts
 pinctrl to bias-bus-hold

On Tue 19 Apr 01:28 CDT 2022, Vijaya Krishna Nivarthi wrote:

> WLAN rail was leaking power during RBSC/sleep even after turning BT off.
> Change sleep pinctrl configuration to handle same.
> 

As I said before, I would like the subject to contain the word
"bluetooth" (or possibly BT if bluetooth doesn't fit).

And drop "arch: " from the subject prefix. If you're uncertain what to
put there, run below command and follow what everyone else does:

  git log --oneline -- arch/arm64/boot/dts/qcom/sc7280-idp.dtsi

> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
> ---
> v4: modify subject of patch to indicate file it is applying to
> v3: apply same change to active state and other sc7280*.dts* as well
> v2: used bias-bus-hold as per review comments
> v1: intial patch used bias-disable for sleep pinctrl in sc7280-idp only
> ---
>  arch/arm64/boot/dts/qcom/sc7280-idp.dtsi | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> index 015a347..85e7467 100644
> --- a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> @@ -400,10 +400,10 @@
>  
>  &qup_uart7_cts {
>  	/*
> -	 * Configure a pull-down on CTS to match the pull of
> -	 * the Bluetooth module.
> +	 * Configure a bias-bus-hold on CTS to lower power usage
> +	 * when BT is turned off.

This comment would just leave a future reader with the question about
_why_ does this lower the power usage...

This problem you're seeing is likely to come back in the next platform
and your successor (or even yourself) will have no use of this comment
to figure out what bias to configure on these pins.

Thanks,
Bjorn

>  	 */
> -	bias-pull-down;
> +	bias-bus-hold;
>  };
>  
>  &qup_uart7_rts {
> @@ -495,10 +495,10 @@
>  		pins = "gpio28";
>  		function = "gpio";
>  		/*
> -		 * Configure a pull-down on CTS to match the pull of
> -		 * the Bluetooth module.
> +		 * Configure a bias-bus-hold on CTS to lower power usage
> +		 * when BT is turned off.
>  		 */
> -		bias-pull-down;
> +		bias-bus-hold;
>  	};
>  
>  	qup_uart7_sleep_rts: qup-uart7-sleep-rts {
> -- 
> Qualcomm INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by the Linux Foundation.
>