linux-kernel - Re: [PATCH 2/2] arm64: dts: qcom: sa8540p-ride: Document i2c busses

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Message-ID: <3d126383-8fea-7ff5-3f42-c131ce46547f@linaro.org>
Date:   Tue, 24 Jan 2023 22:45:57 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Andrew Halaney <ahalaney@...hat.com>, andersson@...nel.org
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,
        bmasney@...hat.com, quic_shazhuss@...cinc.com
Subject: Re: [PATCH 2/2] arm64: dts: qcom: sa8540p-ride: Document i2c busses



On 24.01.2023 20:23, Andrew Halaney wrote:
> It isn't obvious in the current devicetree what is connected. Go ahead
> and document what's on the other end.
> 
> Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
> ---
Other boards do similar things under the i2c host nodes (see
e.g. sm8450-sony-xperia-nagara.dtsi..

> 
> Not sure if this sort of patch is actually welcomed or not but I went
> through this exercise (for the prior patch) and thought it might be
> useful to document.
..and yes it is very welcome!

> 
> Shazad, this also highlights (unless I misread things) that i2c12 has no
> use for us, right? If agreed I can remove it but sorting through the
> lore links that provided all this it seems like at the time it was
> desired to be added.
It's fine if you guys decide that it's useful for some kind expansion
mezzanine or other add-on board, but if it's not connected anywhere
you may wish to disable the host and remove the pinctrl entries, as
keeping it enabled essentially wastes some power.

Konrad
> 
> Thanks,
> Andrew
> 
>  arch/arm64/boot/dts/qcom/sa8540p-ride.dts | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sa8540p-ride.dts b/arch/arm64/boot/dts/qcom/sa8540p-ride.dts
> index cb9fbdeb5a9e..3478ab91fe73 100644
> --- a/arch/arm64/boot/dts/qcom/sa8540p-ride.dts
> +++ b/arch/arm64/boot/dts/qcom/sa8540p-ride.dts
> @@ -317,6 +317,7 @@ &xo_board_clk {
>  
>  &tlmm {
>  	i2c0_default: i2c0-default-state {
> +		/* To USB7002T-I/KDXVA0 USB hub (SIP1 only) */
>  		pins = "gpio135", "gpio136";
>  		function = "qup0";
>  		drive-strength = <2>;
> @@ -324,6 +325,7 @@ i2c0_default: i2c0-default-state {
>  	};
>  
>  	i2c1_default: i2c1-default-state {
> +		/* To PM40028B-F3EI PCIe switch */
>  		pins = "gpio158", "gpio159";
>  		function = "qup1";
>  		drive-strength = <2>;
> @@ -331,6 +333,7 @@ i2c1_default: i2c1-default-state {
>  	};
>  
>  	i2c12_default: i2c12-default-state {
> +		/* Not connected */
>  		pins = "gpio0", "gpio1";
>  		function = "qup12";
>  		drive-strength = <2>;
> @@ -338,6 +341,7 @@ i2c12_default: i2c12-default-state {
>  	};
>  
>  	i2c15_default: i2c15-default-state {
> +		/* To display connector (SIP1 only) */
>  		pins = "gpio36", "gpio37";
>  		function = "qup15";
>  		drive-strength = <2>;
> @@ -345,6 +349,7 @@ i2c15_default: i2c15-default-state {
>  	};
>  
>  	i2c18_default: i2c18-default-state {
> +		/* To ASM330LHH IMU (SIP1 only) */
>  		pins = "gpio66", "gpio67";
>  		function = "qup18";
>  		drive-strength = <2>;