usbotg: otg_set_mode() can only be called once

Christian Eggers ceggers at
Thu Aug 24 05:04:29 PDT 2023

ok, I should better read the manuals ...

"Once a specific mode has been selected it can't be changed later anymore."

In the past I used two OTG cores, one as device and one as host. So both
OTGs were set to a fixed drmode in the device tree.

No I need to implement both features via a single OTG.  But probably
I can use another criteria for choosing the correct boot methods instead of
trying both.

On Thursday, 24 August 2023, 13:30:46 CEST, Christian Eggers wrote:
> Application:
> 1. Try to boot via fastboot (usb device)
> 2. Try to boot via usb drive (usb host)
> Problem:
> barebox at i.MX6ULL:/ setenv otg.mode=host
> imx-usb 2184000.usb at 2184000.of: USB EHCI 1.00
> barebox at i.MX6ULL:/ setenv otg.mode=peripheral
> Cannot set parameter otg.mode: Device or resource busy
> Analysis:
> The otgdev core maintains one `struct otg_mode` per device.  The function
> checks whether the current mode is equal to USB_DR_MODE_OTG.  If not, it
> returns -EBUSY.  There is currently no way to reset the current mode back to
> USB_DR_MODE_OTG after it has been set to peripheral or host mode once.

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