linux-kernel - Re: [PATCH v3 5/5] arm64: dts: qcom: qrb4210-rb2: Enable EUD debug peripheral

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Message-ID: <37603081-e41a-2977-7905-2063abed98cc@linaro.org>
Date:   Thu, 4 May 2023 12:08:50 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bhupesh Sharma <bhupesh.sharma@...aro.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org
Cc:     agross@...nel.org, andersson@...nel.org,
        linux-kernel@...r.kernel.org, bhupesh.linux@...il.com,
        robh+dt@...nel.org, linux-usb@...r.kernel.org,
        krzysztof.kozlowski+dt@...aro.org, krzysztof.kozlowski@...aro.org
Subject: Re: [PATCH v3 5/5] arm64: dts: qcom: qrb4210-rb2: Enable EUD debug
 peripheral



On 4.05.2023 10:26, Bhupesh Sharma wrote:
> Since the USB-C type port on the Qualcomm QRB4210-RB2 board
> can be set primarily in a 'device' configuration (with the default
> DIP switch settings), it makes sense to enable the EUD debug
> peripheral on the board by default by setting the USB 'dr_mode' property
> as 'otg'.
> 
> Now, the EUD debug peripheral can be enabled by executing:
>  $ echo 1 > /sys/bus/platform/drivers/qcom_eud/1610000.eud/enable
> 
> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@...aro.org>
> ---
>  arch/arm64/boot/dts/qcom/qrb4210-rb2.dts | 27 +++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/qrb4210-rb2.dts b/arch/arm64/boot/dts/qcom/qrb4210-rb2.dts
> index 1a0776a0cfd0..0ce72f1ebc10 100644
> --- a/arch/arm64/boot/dts/qcom/qrb4210-rb2.dts
> +++ b/arch/arm64/boot/dts/qcom/qrb4210-rb2.dts
> @@ -30,6 +30,10 @@ vph_pwr: vph-pwr-regulator {
>  	};
>  };
>  
> +&eud {
> +	status = "okay";
> +};
> +
>  &qupv3_id_0 {
>  	status = "okay";
>  };
> @@ -253,7 +257,28 @@ &usb {
>  
>  &usb_dwc3 {
>  	maximum-speed = "super-speed";
> -	dr_mode = "peripheral";
> +
> +	/*
> +	 * There is only one USB DWC3 controller on QRB4210 board and it is connected
> +	 * via a DIP Switch:
> +	 * - to either an USB - C type connector or an USB - A type connector
> +	 *   (via a GL3590-S hub), and
> +	 * - to either an USB - A type connector (via a GL3590-S hub) or a connector
> +	 *   for further connection with a mezzanine board.
> +	 *
> +	 * All of the above hardware muxes would allow us to hook things up in
> +	 * different ways to some potential benefit for static configurations (for e.g.
> +	 * on one hand we can have two USB - A type connectors and a USB - Ethernet
> +	 * connection available and on the other we can use the USB - C type in
> +	 * peripheral mode).
> +	 *
> +	 * Note that since the USB - C type can be used only in peripehral mode,
> +	 * so hardcoding the mode to 'peripheral' here makes sense.
> +	 *
> +	 * However since we want to use the EUD debug device, we set the mode as
> +	 * 'otg' here.
> +	 */
> +	dr_mode = "otg";
So if I understand correctly, EUD works via the type-C connector and
only when the switch is turned such that the type-C connector is in use?

Konrad
>  };
>  
>  &usb_hsphy {