linux-kernel - Re: [PATCH V3 5/7] arm64: dts: qcom: sc7280: Add EUD dt node and dwc3 connector

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Date:   Thu, 6 Jan 2022 16:53:17 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Souradeep Chowdhury <quic_schowdhu@...cinc.com>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, pure.logic@...us-software.ie,
        greg@...ah.com, linux-kernel@...r.kernel.org, tsoni@...eaurora.org,
        psodagud@...eaurora.org, satyap@...eaurora.org,
        pheragu@...eaurora.org, rnayak@...eaurora.org,
        sibis@...eaurora.org, saiprakash.ranjan@...eaurora.org
Subject: Re: [PATCH V3 5/7] arm64: dts: qcom: sc7280: Add EUD dt node and
 dwc3 connector

On Tue 04 Jan 03:58 PST 2022, Souradeep Chowdhury wrote:

> Add the Embedded USB Debugger(EUD) device tree node. The
> node contains EUD base register region and EUD mode
> manager register regions along with the interrupt entry.
> Also add the connector to EUD which is mapped as the child
> of dwc3. The connector is attached to EUD via port. Also add
> the role-switch property to dwc3 node.
> 
> Signed-off-by: Souradeep Chowdhury <quic_schowdhu@...cinc.com>
> ---
>  arch/arm64/boot/dts/qcom/sc7280.dtsi | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> index 53a21d0..2d14e5c 100644
> --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> @@ -1315,6 +1315,18 @@
>  				phys = <&usb_2_hsphy>;
>  				phy-names = "usb2-phy";
>  				maximum-speed = "high-speed";
> +				usb-role-switch;
> +				usb_con: eud_usb_connector {

I think this is backwards.

Iiuc you have dwc3 <-> EUD <-> connector, where the connector typically
would be represented in relation to a Type-C controller.

So I think this graph should be looking something like:


dwc3 {
    ports {
        port {
            dwc3_eud: endpoint {
                remote-endpoint = <&eud_ep>;
            };
        };
    };
};

eud {
    ports {
        port {
            eud_dwc3: endpoint {
                remote-endpoint = <&dwc3_eud>;
            };
        };

        port {
            eud_con: endpoint {
                remote-endpoint = <&con_eud>;
            };
        };
    };
};

connector {
    compatible = "usb-c-connector";

    ports {
        port {
            con_eud: endpoint {
                remote-endpoint = <&eud_con>;
            };
        };
    };
};

With EUD "forwarding" the role switching requests from the connector, or
overriding them if the EUD is enabled.

Alternatively the dwc3 would be in a graph with both the eud and the
connector, but I don't know how to ensure that the EUD decision takes
precedence over the type-c controllers role request...


In the case of us having a type-c controller, such as the pmic_glink,
the connector node would then be a child of the controller.

Regards,
Bjorn

> +					compatible = "qcom,usb-connector-eud",
> +						     "usb-c-connector";
> +					ports {
> +						port@0 {
> +							usb2_role_switch: endpoint {
> +								remote-endpoint = <&eud_ep>;
> +							};
> +						};
> +					};
> +				};
>  			};
>  		};
>  
> @@ -1339,6 +1351,19 @@
>  			interrupts = <GIC_SPI 582 IRQ_TYPE_LEVEL_HIGH>;
>  		};
>  
> +		eud:  eud@...0000 {
> +			compatible = "qcom,sc7280-eud","qcom,eud";
> +			reg = <0 0x88e0000 0 0x2000>,
> +			      <0 0x88e2000 0 0x1000>;
> +			interrupt-parent = <&pdc>;
> +			interrupts = <11 IRQ_TYPE_LEVEL_HIGH>;
> +			port {
> +				eud_ep: endpoint {
> +					remote-endpoint = <&usb2_role_switch>;
> +				};
> +			};
> +		};
> +
>  		nsp_noc: interconnect@...0000 {
>  			reg = <0 0x0a0c0000 0 0x10000>;
>  			compatible = "qcom,sc7280-nsp-noc";
> -- 
> 2.7.4
>