When the USB controller is configured in device mode, and Vbus voltage is varied such that it crosses the Vbus valid threshold multiple times, the ULPI interface becomes unresponsive.
This issue is seen only when the USB controller is operating in device mode and when the Vbus valid threshold is crossed multiple times resulting in generation of Vbus valid interrupts.
The USB controller should ignore these interrupts while operating in device mode as this interrupt is only applicable for A-Type devices while operating in OTG mode.
The following work around must be implemented in the driver to overcome this problem.
When the controller is configured in device mode, the driver should disable Vbus valid interrupts.
Affected: All Zynq-7000 parts.
Resolution: Work-around in the Driver.