Commit [1] enabled the possibility of checking the DVST (Device State
Transition) bit of INTSTS0 (Interrupt Status Register 0) and calling
the irq_dev_state() handler if the DVST bit is set. But neither
commit [1] nor commit [2] actually enabled the DVSE (Device State
Transition Interrupt Enable) bit in the INTENB0 (Interrupt Enable
Register 0). As a consequence, irq_dev_state() handler is getting
called as a side effect of other (non-DVSE) interrupts being fired,
which definitely can't be relied upon, if DVST notifications are of
any value.

Why this doesn't hurt is because usbhsg_irq_dev_state() currently
doesn't do much except of a dev_dbg(). Once more work is added to
the handler (e.g. detecting device "Suspended" state and notifying
other USB gadget components about it), enabling DVSE becomes a hard
requirement. Do it in a standalone commit for better visibility and
clear explanation.

[1] commit f1407d5c ("usb: renesas_usbhs: Add Renesas USBHS common
   code")
[2] commit 2f98382d ("usb: renesas_usbhs: Add Renesas USBHS Gadget")
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Veeraiyan Chidambaram <veeraiyan.chidambaram@in.bosch.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/1568207756-22325-2-git-send-email-external.veeraiyan.c@de.adit-jv.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>