linux-kernel - Re: [PATCH v3 4/4] arm64: dts: qcom: Add base HAMOA-IOT-EVK board

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Message-ID: <cawg456ucsvssm2ngbcjvpprxke7s3sfqf4fzoj5dtfj2flnzw@2e3h5ojgn4s5>
Date: Wed, 30 Jul 2025 21:42:58 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Yijie Yang <yijie.yang@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] arm64: dts: qcom: Add base HAMOA-IOT-EVK board

On Wed, Jul 30, 2025 at 02:28:25PM +0800, Yijie Yang wrote:
> 
> 
> On 2025-07-29 18:37, Dmitry Baryshkov wrote:
> > On Tue, Jul 29, 2025 at 09:32:00AM +0800, Yijie Yang wrote:
> > > The HAMOA-IOT-EVK is an evaluation platform for IoT products, composed of
> > > the Hamoa IoT SoM and a carrier board. Together, they form a complete
> > > embedded system capable of booting to UART.
> > > 
> > > This change enables and overlays the following peripherals on the carrier
> > > board:
> > > - UART
> > > - On-board regulators
> > > - USB Type-C mux
> > > - Pinctrl
> > > - Embedded USB (EUSB) repeaters
> > > - NVMe
> > > - pmic-glink
> > > - USB DisplayPorts
> > > 


> > > +	vreg_rtmr0_1p15: regulator-rtmr0-1p15 {
> > 
> > Hmm, so there are regulators for the retimer, but they are not used.
> > Could you please point out, why?
> 
> According to the schematic, there is a regulator and a retimer (PS8830).
> However, as mentioned above, the retimer is not connected to USB 0 and is
> therefore not used in the EVK. As a result, the regulator is left unused in
> this context.

What is connected to the retimer then?

> 
> > 
> > > +		compatible = "regulator-fixed";
> > > +

[...]

> > > +
> > > +	usb_1_ss0_sbu_default: usb-1-ss0-sbu-state {
> > > +		mode-pins {
> > > +			pins = "gpio166";
> > > +			function = "gpio";
> > > +			bias-disable;
> > > +			drive-strength = <2>;
> > > +			output-high;
> > 
> > What does this pin do? It's not recommended to set GPIO values through
> > pinctrl.
> 
> It is used to switch data lines between USB Type-C orientation detection and
> DisplayPort AUX channels.

I don't think I follow it here. Which data lines? Type-C orientation
detection uses CC1 / CC2, DP AUX use SBU lines.

> When this GPIO is high, USB0 operates in
> orientation detection mode.

What does this mean?

> 
> > 
> > > +		};
> > > +
> > > +		oe-n-pins {
> > > +			pins = "gpio168";
> > > +			function = "gpio";
> > > +			bias-disable;
> > > +			drive-strength = <2>;
> > > +		};
> > > +
> > > +		sel-pins {
> > > +			pins = "gpio167";
> > > +			function = "gpio";
> > > +			bias-disable;
> > > +			drive-strength = <2>;
> > > +		};
> > > +	};
> > > +
> > > +	wcn_bt_en: wcn-bt-en-state {
> > > +		pins = "gpio116";
> > > +		function = "gpio";
> > > +		drive-strength = <2>;
> > > +		bias-disable;
> > > +	};
> > > +
> > > +	wwan_sw_en: wwan-sw-en-state {
> > > +		pins = "gpio221";
> > > +		function = "gpio";
> > > +		drive-strength = <4>;
> > > +		bias-disable;
> > > +	};
> > > +
> > > +	wcn_sw_en: wcn-sw-en-state {
> > > +		pins = "gpio214";
> > > +		function = "gpio";
> > > +		drive-strength = <2>;
> > > +		bias-disable;
> > > +	};
> > > +
> > > +	wcn_usb_sw_n: wcn-usb-sw-n-state {
> > 
> > What does this pin do? Using pinctrl to set GPIO values is not
> > recommended AFAIR.
> 
> This pin functions similarly to usb-1-ss0-sbu-state; it controls the data
> switch between signals from the USB connector and WLAN data.

Could you please explain it? Does it toggle USB2 signals(you've added it
to the USB2 PHY) being routed either to the USB connector or to the WiFi
card? Or do you mean something else?

> > > +&usb_2_hsphy {
> > > +	phys = <&eusb5_repeater>;
> > > +
> > > +	pinctrl-0 = <&wcn_usb_sw_n>;
> > > +	pinctrl-names = "default";
> > > +};
> > > +
> > > +&usb_mp_hsphy0 {
> > > +	phys = <&eusb6_repeater>;
> > > +};
> > > +
> > > +&usb_mp_hsphy1 {
> > > +	phys = <&eusb3_repeater>;
> > > +};
> > > 
> > > -- 
> > > 2.34.1
> > > 
> > 
> 
> -- 
> Best Regards,
> Yijie
> 

-- 
With best wishes
Dmitry