Quoting Stephen Boyd (2016-09-13 18:42:46)
> On the db410c 96boards platform we have a TC7USB40MU[1] on the
> board to mux the D+/D- lines from the SoC between a micro usb
> "device" port and a USB hub for "host" roles. Upon a role switch,
> we need to change this mux to forward the D+/D- lines to either
> the port or the hub. Therefore, introduce a driver for this
> device that intercepts extcon USB_HOST events and logically
> asserts a gpio to mux the "host" D+/D- lines when a host cable is
> attached. When the cable goes away, it will logically deassert
> the gpio and mux the "device" lines.
>
> [1]
> https://toshiba.semicon-storage.com/ap-en/product/logic/bus-switch/detail.TC7USB40MU.html
>
> Cc: MyungJoo Ham <myungjoo....@samsung.com>
> Cc: Chanwoo Choi <cw00.c...@samsung.com>
> Cc: <devicet...@vger.kernel.org>
> Signed-off-by: Stephen Boyd <stephen.b...@linaro.org>
> ---
>
> Should I make the extcon part optional? I could see a case where there are two
> "OTG" ports connected to the mux (or two hubs), and for some reason the
> software may want to mux between them at runtime. If we mandate an extcon,
> that won't be possible to support. Perhaps it would be better to have
> the node, but connect it to the usb controller with a phandle (maybe of_graph
> endpoints would be useful too) so that when the controller wants to mux over
> a port it can do so.
Here's some dts mock-up on top of the db410c for the of_graph stuff. I
haven't written any code around it, but the idea is to allow the binding
to specify how the mux is connected to upstream and downstream D+/D-
lines. This way, we can do some dt parsing of the endpoints and their
parent nodes to figure out if the mux needs to be set high or low to use
a device connector or a usb hub based on if the id cable is present.
Maybe I'm over thinking things though and we could just have a DT
property for that.
soc {
usb@78d9000 {
extcon = <&usb_id>, <&usb_id>;
usb-controller; // needed?
ports {
#address-cells = <1>;
#size-cells = <0>;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
usb_output: endpoint@0 { // USB D+/D-
reg = <0>;
remote-endpoint =
<&usb_switch_input>;
};
};
};
};
};
usb2513 {
compatible = "smsc,usb3503";
reset-gpios = <&pm8916_gpios 3 GPIO_ACTIVE_LOW>;
initial-mode = <1>;
usb-hub; // indicate this is a hub
ports {
#address-cells = <1>;
#size-cells = <0>;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
usb_hub_input: endpoint@0 { // USB{DP,DM}_UP
reg = <0>;
remote-endpoint = <&usb_switch_hub_ep>;
};
usb_hub_output1: endpoint@1 { // USB{DP,DM}_DN1
reg = <1>;
remote-endpoint = <&usb_a2_connector>;
};
usb_hub_output2: endpoint@2 { // USB{DP,DM}_DN2
reg = <2>;
remote-endpoint = <&usb_a1_connector>;
};
usb_hub_output3: endpoint@3 { // USB{DP,DM}_DN3
reg = <3>;
// goes to expansion connector
};
};
};
};
usb_id: usb-id {
compatible = "linux,extcon-usb-gpio";
id-gpio = <&msmgpio 121 GPIO_ACTIVE_HIGH>;
pinctrl-names = "default";
pinctrl-0 = <&usb_id_default>;
};
usb-switch {
compatible = "toshiba,tc7usb40mu";
switch-gpios = <&pm8916_gpios 4 GPIO_ACTIVE_HIGH>;
extcon = <&usb_id>;
pinctrl-names = "default";
pinctrl-0 = <&usb_sw_sel_pm>;
ports {
#address-cells = <1>;
#size-cells = <0>;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
usb_switch_input: endpoint@0 { // D+/D-
reg = <0>;
remote-endpoint = <&usb_output>;
};
usb_switch_device_ep: endpoint@1 { // D1+/D1-
reg = <1>;
remote-endpoint = <&usb_ub_connector>;
};
usb_switch_hub_ep: endpoint@2 { // D2+/D2-
reg = <2>;
remote-endpoint = <&usb_hub_input>;
};
};
};
};
uB-connector {
compatible = "usb-ub-connector";
#address-cells = <1>;
#size-cells = <0>;
usb-connector;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
usb_ub_connector: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_switch_device_ep>;
};
};
};
usb-A-connector1 {
compatible = "usb-A-connector";
#address-cells = <1>;
#size-cells = <0>;
usb-connector;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
usb_a1_connector: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_hub_output2>;
};
};
};
usb-A-connector2 {
compatible = "usb-A-connector";
#address-cells = <1>;
#size-cells = <0>;
usb-connector;
port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
usb_a2_connector: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_hub_output1>;
};
};
};
};
