On Thu, Sep 22, 2016 at 11:51:02AM -0700, Stephen Boyd wrote:

Quoting Peter Chen (2016-09-16 18:16:05)

quoted

On Wed, Sep 14, 2016 at 01:55:02AM -0700, Stephen Boyd wrote:

quoted

Quoting Stephen Boyd (2016-09-13 18:42:46)

quoted

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: <redacted>
Signed-off-by: Stephen Boyd <redacted>
---

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?

This was already in the dts files for db410c. In the chipidea binding
one is for EXTCON_USB (vbus) and one is for EXTCON_USB_HOST (id). My
understanding is that extcon-usb-gpio.c sends events for both EXTCON_USB
and EXTCON_USB_HOST when the gpio changes state. vbus detection is not
that great on this board because we only have on gpio for this.

I think extcon-usb-gpio.c needs to extend for supporting vbus event,
otherwise, the micro-b cable's connect/disconnect will introduce
EXTCON_USB_HOST event, if you use two <&usb_idx> for both id and
vbus event.

-- 

Best Regards,
Peter Chen