topic Generate USB device detach event in i.MX Processors

Generate USB device detach event

falstaff — Wed, 16 Aug 2017 21:36:44 GMT

Using U-Boot's USB Gadget stack for a USB client protocol implementation generates a proper USB disconnect on i.MX 6 devices, however, on i.MX 7 it does not generate a USB disconnect. This seem to cause issues on some hosts for subsequent USB reenumeration, hence I am trying to understand why i.MX 7 behaves differently.

As far as I understand the USB disconnect is generated by udc_disconnect in drivers/usb/gadget/ci_udc.c by writing a 0 to USBCMD RS field. According to the i.MX 6 and 7 Reference Manual this should cause a disconnect

Device operation mode:
Writing a one to this bit will cause the controller to enable a pull-up on D+ and initiate an attach event. This
control bit is not directly connected to the pull-up enable, as the pull-up will become disabled upon
transitioning into high-speed mode. Software should use this bit to prevent an attach event before the
controller has been properly initialized. Writing a 0 to this will cause a detach event.

It just seems that this does not work on i.MX 7... How can I properly cause a detach even on i.MX 7?

What I also noticed is that in the i.MX 7 Reference Manaul some register are described in the USB-PHY chapter 11.5, however, a register map for the USB PHY seems to be missing....

Best regards

Stefan

Re: Generate USB device detach event

CarlosCasillas — Wed, 23 Aug 2017 05:31:57 GMT

Hi Stefan,

Could you please specify which NXP boards and BSP are you using? Have you ensured that you are testing the same kind of USB port on both devices (Host only / OTG, with/without PHY).

Hope this will be useful for you.

Best regards!

/Carlos

Re: Generate USB device detach event

falstaff — Mon, 28 Aug 2017 20:07:25 GMT

This is on our Toradex Colibri iMX6/iMX7 boards. I can replicate the issue on GA 4.1.15_2..0.0 as well as on mainline, it is not really software related, since I can reproduce it when poking the register using U-Boot memory write (mw.l) commands directly.

I am especially wondering where the registers documented in i.MX 7 Reference Manaul in the USB-PHY chapter 11.5 actually are located...