ENGR00211686 mx6 usb: system crash after suspend/resume
- the pre-condition of this issue is:
1. usb gadget must be probed before usb host
2. usb otg must be in host mode
- the root cause of this issue is
because of the issue of week 2p5, a vbus change interrupt will
be issued when system enter into DSM, which will cause system
exit DSM, so we have a walk aroud to disable usb vbus change
interrupt when system enter into DSM.
But this walk around just provent the interrupt generating, the
vbus change status is still on. When usb gadget is probed, the
vbus change interrupt will be enabled by its resume interface by
mistake, and then continuous interrupt will be generated because
usb otg is in host mode, it can't clear the vbus change status.
The system have a protect mechanism that when one IRQ's handler
return IRQ_NONE more than 99000 times, it will through a exception
to inform such situation. That's the reason why system crash.
Signed-off-by: Tony LIU <junjie.liu@freescale.com>