usb: chipidea: udc: fix the oops after rmmod gadget

When we rmmod gadget, the ci->driver needs to be cleared.
Otherwise, when we plug in usb cable again, the driver will
consider gadget is there, and go to enumeration procedure,
but in fact, it was removed.

ci_hdrc ci_hdrc.0: Connected to host
Unable to handle kernel paging request at virtual address 7f02a42c
pgd = 80004000
[7f02a42c] *pgd=3f13d811, *pte=00000000, *ppte=00000000
Internal error: Oops: 7 [#1] SMP ARM
Modules linked in: usb_f_acm u_serial libcomposite configfs [last unloaded: g_serial]
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0+ #42
task: 807dba88 ti: 807d0000 task.ti: 807d0000
PC is at udc_irq+0x8fc/0xea4
LR is at l2x0_cache_sync+0x5c/0x6c
pc : [<803de7f4>]    lr : [<8001d0f0>]    psr: 20000193
sp : 807d1d98  ip : 807d1d80  fp : 807d1df4
r10: af809900  r9 : 808184d4  r8 : 00080001
r7 : 00082001  r6 : afb711f8  r5 : afb71010  r4 : ffffffea
r3 : 7f02a41c  r2 : afb71010  r1 : 807d1dc0  r0 : afb71068
Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: 10c53c7d  Table: 3f01804a  DAC: 00000017
Process swapper/0 (pid: 0, stack limit = 0x807d0238)
Stack: (0x807d1d98 to 0x807d2000)
1d80:                                                       00000000 afb71014
1da0: 000040f6 00000000 00000001 00000000 00007530 00000000 afb71010 001dcd65
1dc0: 01000680 00400000 807d1e2c afb71010 0000004e 00000000 00000000 0000004b
1de0: 808184d4 af809900 807d1e0c 807d1df8 803dbc24 803ddf04 afba75c0 0000004e
1e00: 807d1e44 807d1e10 8007a19c 803dbb9c 8108e7e0 8108e7e0 9ceddce0 af809900
1e20: 0000004e 807d0000 0000004b 00000000 00000010 00000000 807d1e5c 807d1e48
1e40: 8007a334 8007a154 af809900 0000004e 807d1e74 807d1e60 8007d3b4 8007a2f0
1e60: 0000004b 807cce3c 807d1e8c 807d1e78 80079b08 8007d300 00000180 807d8ba0
1e80: 807d1eb4 807d1e90 8000eef4 80079aec 00000000 f400010c 807d8ce4 807d1ed8
1ea0: f4000100 96d5c75d 807d1ed4 807d1eb8 80008600 8000eeac 8042699c 60000013
1ec0: ffffffff 807d1f0c 807d1f54 807d1ed8 8000e180 800085dc 807d1f20 00000046
1ee0: 9cedd275 00000010 8108f080 807de294 00000001 807de248 96d5c75d 00000010
1f00: 00000000 807d1f54 00000000 807d1f20 8005ff54 8042699c 60000013 ffffffff
1f20: 9cedd275 00000010 00000005 8108f080 8108f080 00000001 807de248 8086bd00
1f40: 807d0000 00000001 807d1f7c 807d1f58 80426af0 80426950 807d0000 00000000
1f60: 808184c0 808184c0 807d8954 805b886c 807d1f8c 807d1f80 8000f294 80426a44
1f80: 807d1fac 807d1f90 8005f110 8000f288 807d1fac 807d8908 805b4748 807dc86c
1fa0: 807d1fbc 807d1fb0 805aa58c 8005f068 807d1ff4 807d1fc0 8077c860 805aa530
1fc0: ffffffff ffffffff 8077c330 00000000 00000000 807bef88 00000000 10c53c7d
1fe0: 807d88d0 807bef84 00000000 807d1ff8 10008074 8077c594 00000000 00000000
Backtrace:
[<803ddef8>] (udc_irq+0x0/0xea4) from [<803dbc24>] (ci_irq+0x94/0x14c)
[<803dbb90>] (ci_irq+0x0/0x14c) from [<8007a19c>] (handle_irq_event_percpu+0x54/0x19c)
 r5:0000004e r4:afba75c0
 [<8007a148>] (handle_irq_event_percpu+0x0/0x19c) from [<8007a334>] (handle_irq_event+0x50/0x70)
[<8007a2e4>] (handle_irq_event+0x0/0x70) from [<8007d3b4>] (handle_fasteoi_irq+0xc0/0x16c)
 r5:0000004e r4:af809900
 [<8007d2f4>] (handle_fasteoi_irq+0x0/0x16c) from [<80079b08>] (generic_handle_irq+0x28/0x38)
 r5:807cce3c r4:0000004b
 [<80079ae0>] (generic_handle_irq+0x0/0x38) from [<8000eef4>] (handle_IRQ+0x54/0xb4)
 r4:807d8ba0 r3:00000180
 [<8000eea0>] (handle_IRQ+0x0/0xb4) from [<80008600>] (gic_handle_irq+0x30/0x64)
 r8:96d5c75d r7:f4000100 r6:807d1ed8 r5:807d8ce4 r4:f400010c
 r3:00000000
 [<800085d0>] (gic_handle_irq+0x0/0x64) from [<8000e180>] (__irq_svc+0x40/0x54)
Exception stack(0x807d1ed8 to 0x807d1f20)
1ec0:                                                       807d1f20 00000046
1ee0: 9cedd275 00000010 8108f080 807de294 00000001 807de248 96d5c75d 00000010
1f00: 00000000 807d1f54 00000000 807d1f20 8005ff54 8042699c 60000013 ffffffff
 r7:807d1f0c r6:ffffffff r5:60000013 r4:8042699c
 [<80426944>] (cpuidle_enter_state+0x0/0xf4) from [<80426af0>] (cpuidle_idle_call+0xb8/0x174)
 r9:00000001 r8:807d0000 r7:8086bd00 r6:807de248 r5:00000001
 r4:8108f080
 [<80426a38>] (cpuidle_idle_call+0x0/0x174) from [<8000f294>] (arch_cpu_idle+0x18/0x5c)
[<8000f27c>] (arch_cpu_idle+0x0/0x5c) from [<8005f110>] (cpu_startup_entry+0xb4/0x148)
[<8005f05c>] (cpu_startup_entry+0x0/0x148) from [<805aa58c>] (rest_init+0x68/0x80)
 r7:807dc86c
 [<805aa524>] (rest_init+0x0/0x80) from [<8077c860>] (start_kernel+0x2d8/0x334)
[<8077c588>] (start_kernel+0x0/0x334) from [<10008074>] (0x10008074)
Code: e59031e0 e51b203c e24b1034 e2820058 (e5933010)
---[ end trace f874b2c5533c04bc ]---
Kernel panic - not syncing: Fatal exception in interrupt

Tested-by: Marek Vasut <marex@denx.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/chipidea/udc.c

@@ -1667,13 +1667,13 @@ static int ci_udc_stop(struct usb_gadget *gadget,
 		if (ci->platdata->notify_event)
 			ci->platdata->notify_event(ci,
 			CI_HDRC_CONTROLLER_STOPPED_EVENT);
-		ci->driver = NULL;
 		spin_unlock_irqrestore(&ci->lock, flags);
 		_gadget_stop_activity(&ci->gadget);
 		spin_lock_irqsave(&ci->lock, flags);
 		pm_runtime_put(&ci->gadget.dev);
 	}
 
+	ci->driver = NULL;
 	spin_unlock_irqrestore(&ci->lock, flags);
 
 	return 0;