Messages in this thread | | | Date | Mon, 13 Jul 2015 12:14:43 -0700 | Subject | Re: [PATCH v3 00/11] USB: OTG/DRD Core functionality | From | Andrew Bresticker <> |
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Hi Roger,
On Wed, Jul 8, 2015 at 3:19 AM, Roger Quadros <rogerq@ti.com> wrote: > Usage model: > ----------- > > - The OTG controller device is assumed to be the parent of > the host and gadget controller. It must call usb_otg_register() > before populating the host and gadget devices so that the OTG > core is aware that it is an OTG device before the host & gadget > register. The OTG controller must provide struct otg_fsm_ops * > which will be called by the OTG core depending on OTG bus state.
I'm wondering if the requirement that the OTG controller be the parent of the USB host/device-controllers makes sense. For some context, I'm working on adding dual-role support for Tegra210, specifically on a system with USB Type-C. On Tegra, the USB host-controller and USB device-controller are two separate IP blocks (XUSB host and XUSB device) with another, separate, IP block (XUSB padctl) for the USB PHY and OTG support. In the non-Type-C case, your OTG framework could work well, though it's debatable as to whether or not the XUSB padctl device should be a parent to the XUSB host/device-controller devices (currently it isn't - it's just a PHY provider). But in the Type-C case, it's an off-chip embedded controller that determines the dual-role status of the Type-C port, so the above requirement doesn't make sense at all.
My idea was to have the OTG/DRD controller explicitly specify its host and device controllers, so in DT, something like:
otg-controller { ... device-controller = <&usb_device>; host-controller = <&usb_host>; ... };
usb_device: usb-device@.... { ... };
usb_host: usb-host@... { ... };
What do you think?
Thanks, Andrew
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