linux-kernel - Re: [PATCH 3/4] arm64: dts: qcom: qcm6490-fairphone-fp5: Enable CCI pull-up

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Message-ID: <1be80052-3ba5-46de-804a-de995f8db5d4@oss.qualcomm.com>
Date: Thu, 2 Oct 2025 14:45:49 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Griffin Kroah-Hartman <griffin.kroah@...rphone.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>, devicetree@...r.kernel.org,
        Daniel Scally <djrscally@...il.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        André Apitzsch
 <git@...tzsch.eu>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Wolfram Sang <wsa@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 3/4] arm64: dts: qcom: qcm6490-fairphone-fp5: Enable CCI
 pull-up

On 10/2/25 12:15 PM, Griffin Kroah-Hartman wrote:
> Enable vreg_l6p which is used as a pull-up for the CCI busses, to make
> sure I2C communication works as expected.
> 
> Signed-off-by: Griffin Kroah-Hartman <griffin.kroah@...rphone.com>
> ---

Makes me wonder if we should maybe extend the CCI definition
(or maybe the common i2c-bus binding?) to accept an external
pull-up supply, as this is a common problem.. (+Bryan, Wolfram)

We could then shut down the regulator when cameras are not
in use, preserving some trace amounts of power.

Or maybe L6P is already used as a pull-up supply for more things
onboard and should be always-on either way? Could you please
check that, Griffin?

Konrad

>  arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts b/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
> index e115b6a52b299ef663ccfb614785f8f89091f39d..2dd2c452592aa6b0ac826f19eb9cb1a8b90cee47 100644
> --- a/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
> +++ b/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
> @@ -749,6 +749,8 @@ vreg_l6p: ldo6 {
>  				regulator-name = "vreg_l6p";
>  				regulator-min-microvolt = <1700000>;
>  				regulator-max-microvolt = <1904000>;
> +				/* Pull-up for CCI I2C busses */
> +				regulator-always-on;
>  			};
>  
>  			vreg_l7p: ldo7 {
>