Re: [RFC/PATCH] usb: misc: Add a driver for TC7USB40MU

[Peter Chen <hzpeterchen@gmail.com>]

On Wed, Sep 14, 2016 at 01:55:02AM -0700, Stephen Boyd wrote:
> 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.ham@samsung.com>
> > Cc: Chanwoo Choi <cw00.choi@samsung.com>
> > Cc: <devicetree@vger.kernel.org>
> > Signed-off-by: Stephen Boyd <stephen.boyd@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>;

Why you have two same extcon phandler? From my mind, one should id,
another should is vbus. Besides, I find extcon-usb-gpio.c is lack of
vbus support, how you support vbus detection for
connection/disconnection with PC for your chipidea msm patch set?

> 			usb-controller; // needed?

Not needed. You only need to describe controller, mux ic, and hub 
(if you need platform stuffs the driver needs to know).

Peter
> 
> 			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>;
> 			};
> 		};
> 	};
> };
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-- 

Best Regards,
Peter Chen