usb: chipidea: debug: disable usb irq while role switch

commit 251b3c8b upstream.

Since the ci->role will be set after the host role start is complete, there
will be nobody cared irq during start host if usb irq enabled. This error
can be reproduced on i.mx6 sololite EVK board by:
1. disable otg id irq(IDIE) and disable all real otg properties of usbotg1
   in dts.
2. boot up the board with ID cable and usb device connected.
3. echo gadget > /sys/kernel/debug/ci_hdrc.0/role
4. echo host > /sys/kernel/debug/ci_hdrc.0/role
5. irq 212: nobody cared.
Signed-off-by: Li Jun <jun.li@freescale.com>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/usb/chipidea/debug.c

@@ -312,8 +312,10 @@ static ssize_t ci_role_write(struct file *file, const char __user *ubuf,
 	if (role == CI_ROLE_END || role == ci->role)
 		return -EINVAL;
 
+	disable_irq(ci->irq);
 	ci_role_stop(ci);
 	ret = ci_role_start(ci, role);
+	enable_irq(ci->irq);
 
 	return ret ? ret : count;
 }