Re: [PATCH v2 1/2] dt-bindings: usb: Introduce GPIO-based SBU mux

Bjorn Andersson
2023-01-18T18:09:13Z

On Tue, Jan 17, 2023 at 11:56:57AM -0600, Rob Herring wrote:
> On Thu, Jan 12, 2023 at 08:11:14PM -0800, Bjorn Andersson wrote:
> > From: Bjorn Andersson <bjorn.andersson@linaro.org>
> >
> > Introduce a binding for GPIO-based mux hardware used for connecting,
> > disconnecting and switching orientation of the SBU lines in USB Type-C
> > applications.
> >
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> > Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
> > ---
> >
> > Changes since v1:
> > - Expanded the example to indicate how this fits with the TCPM
> > - Updated maintainer email address.
> >
> > .../devicetree/bindings/usb/gpio-sbu-mux.yaml | 110 ++++++++++++++++++
> > 1 file changed, 110 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml b/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml
> > new file mode 100644
> > index 000000000000..bf4b1d016e1f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/usb/gpio-sbu-mux.yaml
> > @@ -0,0 +1,110 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: "http://devicetree.org/schemas/usb/gpio-sbu-mux.yaml#"
> > +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> > +
> > +title: GPIO-based SBU mux
> > +
> > +maintainers:
> > + - Bjorn Andersson <andersson@kernel.org>
> > +
> > +description:
> > + In USB Type-C applications the SBU lines needs to be connected, disconnected
> > + and swapped depending on the altmode and orientation. This binding describes
> > + a family of hardware solutions which switches between these modes using GPIO
> > + signals.
> > +
> > +properties:
> > + compatible:
> > + items:
> > + - enum:
> > + - onnn,fsusb43l10x
> > + - pericom,pi3usb102
> > + - const: gpio-sbu-mux
> > +
> > + enable-gpios:
> > + description: Switch enable GPIO
> > +
> > + select-gpios:
> > + description: Orientation select
> > +
> > + vcc-supply:
> > + description: power supply
> > +
> > + mode-switch:
> > + description: Flag the port as possible handle of altmode switching
> > + type: boolean
> > +
> > + orientation-switch:
> > + description: Flag the port as possible handler of orientation switching
> > + type: boolean
> > +
> > + port:
> > + $ref: /schemas/graph.yaml#/properties/port
> > + description:
> > + A port node to link the SBU mux to a TypeC controller for the purpose of
> > + handling altmode muxing and orientation switching.
> > +
> > +required:
> > + - compatible
> > + - enable-gpios
> > + - select-gpios
> > + - mode-switch
> > + - orientation-switch
> > + - port
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + #include <dt-bindings/gpio/gpio.h>
> > +
> > + tcpm {
> > + connector {
> > + compatible = "usb-c-connector";
> > +
> > + ports {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + port@0 {
> > + reg = <0>;
> > + tcpm_hs_out: endpoint {
> > + remote-endpoint = <&usb_hs_phy_in>;
> > + };
> > + };
> > +
> > + port@1 {
> > + reg = <1>;
> > + tcpm_ss_out: endpoint {
> > + remote-endpoint = <&usb_ss_phy_in>;
> > + };
> > + };
> > +
> > + port@2 {
> > + reg = <2>;
> > + tcpm_sbu_out: endpoint {
> > + remote-endpoint = <&sbu_mux_in>;
> > + };
> > + };
> > + };
> > + };
> > + };
> > +
> > + sbu-mux {
> > + compatible = "pericom,pi3usb102", "gpio-sbu-mux";
> > +
> > + enable-gpios = <&tlmm 101 GPIO_ACTIVE_LOW>;
> > + select-gpios = <&tlmm 164 GPIO_ACTIVE_HIGH>;
> > +
> > + mode-switch;
> > + orientation-switch;
> > +
> > + port {
> > + sbu_mux_in: endpoint {
> > + remote-endpoint = <&tcpm_sbu_out>;
> > + };
>
> Don't you need a connection to whatever drives SBU? Maybe your case is
> fixed because the phy does the DP/USB muxing? But the binding needs to
> support the worst case which I guess would be all the muxing/switching
> is done by separate board level components.
>

Perhaps I'm misunderstanding your request, but I think this is the worst
case you're talking about.

&usb_ss_phy_in is a reference to the PHY, which does switching/muxing of
the SuperSpeed lanes in the connector, but the PHY provides no control
over the SBU signals.

So this sbu-mux is a separate component between the SBU-pads on the SoC
and the usb-c-connector, referenced through he &sbu_mux_in reference.

So upon e.g. a orientation switch, the typec_switch_set() call the tcpm
implementation will request orientation switching from port@1 and port@2
(no orientation-switch on port@0/HS pins).

Regards,
Bjorn