usb: echi-hcd: Add ehci_setup check before echi_shutdown

This patch protects system from crashing at shutdown in
cases where usb host is not added yet from OTG controller driver.
As ehci_setup() not done yet, so stop accessing registers or
variables initialized as part of ehci_setup().

The use case is simple, for boards like DB410c where the usb host
or device functionality is decided based on the micro-usb cable
presence. If the board boots up with micro-usb connected, the
OTG driver like echi-msm would not add the usb host by default.
However a system shutdown would go and access registers and
uninitialized variables, resulting in below crash.

Unable to handle kernel NULL pointer dereference at virtual address
 00000008
pgd = ffffffc034581000
[00000008] *pgd=0000000000000000, *pud=0000000000000000
CPU: 2 PID: 1957 Comm: reboot Not tainted 4.6.0+ #99
task: ffffffc034bc0000 ti: ffffffc0345cc000 task.ti: ffffffc0345cc000
PC is at ehci_halt+0x54/0x108
LR is at ehci_halt+0x38/0x108
pc : [<ffffff800869837c>] lr : [<ffffff8008698360>] pstate: a00001c5
sp : ffffffc0345cfc60
x29: ffffffc0345cfc60 x28: ffffffc0345cc000
x27: ffffff8008a4d000 x26: 000000000000008e
x25: ffffff8008d86cb0 x24: ffffff800908b040
x23: ffffffc036068870 x22: ffffff8009d0a000
x21: ffffffc03512a410 x20: ffffffc03512a410
x19: ffffffc03512a338 x18: 00000000000065ba
x17: ffffff8009b16b80 x16: 0000000000000003
x15: 00000000000065b9 x14: 00000000000065b6
x13: 0000000000000000 x12: 0000000000000000
x11: 000000000000003d x10: ffffffc0345cf9e0
x9 : 0000000000000001 x8 : ffffffc0345cc000
x7 : ffffff8008698360 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001
x3 : 0000000000000000 x2 : 0000000000000000
x1 : 0000000000000008 x0 : ffffffc034bc0000

Process reboot (pid: 1957, stack limit = 0xffffffc0345cc020)
Stack: (0xffffffc0345cfc60 to 0xffffffc0345d0000)
fc60: ffffffc0345cfc90 ffffff8008698448 ffffffc03512a338 ffffffc03512a338
fc80: ffffffc03512a410 ffffff8008a3bbfc ffffffc0345cfcc0 ffffff8008698548
fca0: ffffffc03512a338 ffffffc03512a000 ffffffc03512a410 ffffff8009d0a000
fcc0: ffffffc0345cfcf0 ffffff800865d2bc ffffffc036068828 ffffffc036068810
fce0: ffffffc036003810 ffffff800853f43c ffffffc0345cfd00 ffffff800854338c
fd00: ffffffc0345cfd10 ffffff800853f45c ffffffc0345cfd60 ffffff80080e0f48
fd20: 0000000000000000 0000000001234567 ffffff8008f8c000 ffffff8008f8c060
fd40: 0000000000000000 0000000000000015 0000000000000120 ffffff80080e0f30
fd60: ffffffc0345cfd70 ffffff80080e1020 ffffffc0345cfd90 ffffff80080e12fc
fd80: 0000000000000000 0000000001234567 0000000000000000 ffffff8008085e70
fda0: 0000000000000000 0000005592905000 ffffffffffffffff 0000007f79daf1cc
fdc0: 0000000000000000 0000000000000000 0000007ffcbb1198 000000000000000a
fde0: 00000055928d3f58 0000000000000001 ffffffc034900000 00000000fffffffe
fe00: ffffffc034900000 0000007f79da902c ffffffc0345cfe40 ffffff800820af38
fe20: 0000000000000000 0000007ffcbb1078 ffffffffffffffff ffffff80081e9b38
fe40: ffffffc0345cfe60 ffffff80081eb410 ffffffc0345cfe60 ffffff80081eb444
fe60: ffffffc0345cfec0 ffffff80081ec4f4 0000000000000000 0000007ffcbb1078
fe80: ffffffffffffffff 0000000000000015 ffffffc0345cfec0 0000007ffcbb1078
fea0: 0000000000000002 000000000000000a ffffffffffffffff 0000000000000000
fec0: 0000000000000000 ffffff8008085e70 fffffffffee1dead 0000000028121969
fee0: 0000000001234567 0000000000000000 ffffffffffffffff 8080800000800000
ff00: 0000800000808080 0000007ffcbb10f0 000000000000008e fefeff54918cb8c7
ff20: 7f7f7f7fffffffff 0101010101010101 0000000000000010 0000000000000000
ff40: 0000000000000000 0000007f79e33588 0000005592905eb8 0000007f79daf1b0
ff60: 0000007ffcbb1340 0000005592906000 0000005592905000 0000005592906000
ff80: 0000005592907000 0000000000000002 0000007ffcbb1d98 0000005592906000
ffa0: 00000055928d2000 0000000000000000 0000000000000000 0000007ffcbb1aa0
ffc0: 00000055928b819c 0000007ffcbb1aa0 0000007f79daf1cc 0000000000000000
ffe0: fffffffffee1dead 000000000000008e 05ef555057155555 d555544d55d775d3
Call trace:
Exception stack(0xffffffc0345cfaa0 to 0xffffffc0345cfbc0)
Set corner to 6
faa0: ffffffc03512a338 ffffffc03512a410 ffffffc0345cfc60 ffffff800869837c
fac0: ffffff8008114210 0000000100000001 ffffff8009ce1b20 ffffff8009ce5f20
fae0: ffffffc0345cfb80 ffffff80081145a8 ffffffc0345cfc10 ffffff800810b924
fb00: ffffffc0345cc000 00000000000001c0 ffffffc03512a410 ffffff8009d0a000
fb20: ffffffc036068870 ffffff800908b040 ffffff8008d86cb0 000000000000008e
fb40: ffffffc034bc0000 0000000000000008 0000000000000000 0000000000000000
fb60: 0000000000000001 0000000000000080 0000000000000000 ffffff8008698360
fb80: ffffffc0345cc000 0000000000000001 ffffffc0345cf9e0 000000000000003d
fba0: 0000000000000000 0000000000000000 00000000000065b6 00000000000065b9
[<ffffff800869837c>] ehci_halt+0x54/0x108
[<ffffff8008698448>] ehci_silence_controller+0x18/0xcc
[<ffffff8008698548>] ehci_shutdown+0x4c/0x64
[<ffffff800865d2bc>] usb_hcd_platform_shutdown+0x1c/0x24
[<ffffff800854338c>] platform_drv_shutdown+0x20/0x28
[<ffffff800853f45c>] device_shutdown+0xf4/0x1b0
[<ffffff80080e0f48>] kernel_restart_prepare+0x34/0x3c
[<ffffff80080e1020>] kernel_restart+0x14/0x74
[<ffffff80080e12fc>] SyS_reboot+0x110/0x21c
[<ffffff8008085e70>] el0_svc_naked+0x24/0x28
Code: 53001c42 350000a2 d5033e9f 91002021 (b9000022)

Fixes 4bb3cad7 ("usb: host: ehci-msm: Register usb shutdown function")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Tested-by: Pramod Gurav <pramod.gurav@linaro.org>
Tested-by: Andy Gross <andy.gross@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-hcd.c

@@ -368,6 +368,15 @@ static void ehci_shutdown(struct usb_hcd *hcd)
 {
 	struct ehci_hcd	*ehci = hcd_to_ehci(hcd);
 
+	/**
+	 * Protect the system from crashing at system shutdown in cases where
+	 * usb host is not added yet from OTG controller driver.
+	 * As ehci_setup() not done yet, so stop accessing registers or
+	 * variables initialized in ehci_setup()
+	 */
+	if (!ehci->sbrn)
+		return;
+
 	spin_lock_irq(&ehci->lock);
 	ehci->shutdown = true;
 	ehci->rh_state = EHCI_RH_STOPPING;