usb: dwc3: core: Fix gadget for system suspend/resume

During system resume, if the event buffers are not setup before
the gadget controller starts then we start with invalid context
and this can lead to bus access errors. This is especially true for
platforms that loose the controller context during system suspend.
e.g. AM437x.

The following backtrace was found when the system is suspended
and resumed with g_zero loaded on AM437x-evm (USB cable connected
to host all the while).

[  120.981506] WARNING: CPU: 0 PID: 1656 at drivers/bus/omap_l3_noc.c:137 l3_interrupt_handler+0x198/0x28c()
[  120.981514] L3 custom error: MASTER:USB0 WR TARGET:GPMC
[  120.981638] Modules linked in: g_mass_storage usb_f_mass_storage libcomposite configfs bufferclass_ti(O) omaplfb(O) cryptodev(O) dwc3 snd_soc_evm snd_soc_omap snd_pe
[  120.981659] CPU: 0 PID: 1656 Comm: sh Tainted: G           O 3.12.10-gc559824 #1
[  120.981669] Backtrace:
[  120.981705] [<c0017880>] (dump_backtrace+0x0/0x10c) from [<c0017a1c>] (show_stack+0x18/0x1c)
[  120.981730]  r6:c02819ac r5:00000009 r4:ec137cb8 r3:00000000
[  120.981767] [<c0017a04>] (show_stack+0x0/0x1c) from [<c056c0b0>] (dump_stack+0x20/0x28)
[  120.981802] [<c056c090>] (dump_stack+0x0/0x28) from [<c0046d08>] (warn_slowpath_common+0x70/0x90)
[  120.981830] [<c0046c98>] (warn_slowpath_common+0x0/0x90) from [<c0046dcc>] (warn_slowpath_fmt+0x38/0x40)
[  120.981856]  r8:c0855eb0 r7:00000002 r6:f1000700 r5:00000007 r4:80080003
[  120.981886] [<c0046d94>] (warn_slowpath_fmt+0x0/0x40) from [<c02819ac>] (l3_interrupt_handler+0x198/0x28c)
[  120.981900]  r3:c0801ab8 r2:c06cb354
[  120.981936] [<c0281814>] (l3_interrupt_handler+0x0/0x28c) from [<c007162c>] (handle_irq_event_percpu+0x54/0x1b8)
[  120.981962] [<c00715d8>] (handle_irq_event_percpu+0x0/0x1b8) from [<c00717c0>] (handle_irq_event+0x30/0x40)
[  120.981993] [<c0071790>] (handle_irq_event+0x0/0x40) from [<c0074058>] (handle_fasteoi_irq+0x74/0x128)
[  120.982006]  r4:ed0056c0 r3:00000000
[  120.982033] [<c0073fe4>] (handle_fasteoi_irq+0x0/0x128) from [<c0070f34>] (generic_handle_irq+0x28/0x38)
[  120.982046]  r4:0000002a r3:c0073fe4
[  120.982085] [<c0070f0c>] (generic_handle_irq+0x0/0x38) from [<c0015560>] (handle_IRQ+0x38/0x8c)
[  120.982098]  r4:c080137c r3:00000182
[  120.982124] [<c0015528>] (handle_IRQ+0x0/0x8c) from [<c00087e0>] (gic_handle_irq+0x30/0x5c)
[  120.982145]  r6:ec137dd0 r5:c07ac480 r4:fa24010c r3:00000100
[  120.982169] [<c00087b0>] (gic_handle_irq+0x0/0x5c) from [<c056fcc0>] (__irq_svc+0x40/0x54)
[  120.982179] Exception stack(0xec137dd0 to 0xec137e18)
[  120.982195] 7dc0:                                     00000000 a00001d3 00000000 00000004
[  120.982216] 7de0: a0000153 ec1d9010 c080de90 ec137e30 c080debc 00000000 ed756e44 ec137e2c
[  120.982232] 7e00: ec137de0 ec137e18 bf1150e4 bf115474 60000153 ffffffff
[  120.982253]  r7:ec137e04 r6:ffffffff r5:60000153 r4:bf115474
[  120.982327] [<bf115438>] (dwc3_complete+0x0/0x40 [dwc3]) from [<c0338f50>] (dpm_complete+0xd4/0x19c)
[  120.982341]  r5:ed756e10 r4:ed756e64
[  120.982370] [<c0338e7c>] (dpm_complete+0x0/0x19c) from [<c0339034>] (dpm_resume_end+0x1c/0x20)
[  120.982400] [<c0339018>] (dpm_resume_end+0x0/0x20) from [<c006d4ec>] (suspend_devices_and_enter+0x118/0x33c)
[  120.982412]  r4:c0833da4 r3:00000000
[  120.982436] [<c006d3d4>] (suspend_devices_and_enter+0x0/0x33c) from [<c006d928>] (pm_suspend+0x218/0x254)
[  120.982458] [<c006d710>] (pm_suspend+0x0/0x254) from [<c006c594>] (state_store+0x70/0xc0)
[  120.982478]  r6:c057a6cc r5:c06a8320 r4:00000003 r3:0000006d
[  120.982515] [<c006c524>] (state_store+0x0/0xc0) from [<c0264cc0>] (kobj_attr_store+0x1c/0x28)
[  120.982546] [<c0264ca4>] (kobj_attr_store+0x0/0x28) from [<c012ccb8>] (sysfs_write_file+0x170/0x1a4)
[  120.982583] [<c012cb48>] (sysfs_write_file+0x0/0x1a4) from [<c00d17e4>] (vfs_write+0xb8/0x190)
[  120.982611] [<c00d172c>] (vfs_write+0x0/0x190) from [<c00d1bf8>] (SyS_write+0x44/0x78)
[  120.982641] [<c00d1bb4>] (SyS_write+0x0/0x78) from [<c0014660>] (ret_fast_syscall+0x0/0x30)

Signed-off-by: Roger Quadros <rogerq@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.c

@@ -821,6 +821,7 @@ static void dwc3_complete(struct device *dev)
 
 	spin_lock_irqsave(&dwc->lock, flags);
 
+	dwc3_event_buffers_setup(dwc);
 	switch (dwc->dr_mode) {
 	case USB_DR_MODE_PERIPHERAL:
 	case USB_DR_MODE_OTG:
@@ -828,7 +829,6 @@ static void dwc3_complete(struct device *dev)
 		/* FALLTHROUGH */
 	case USB_DR_MODE_HOST:
 	default:
-		dwc3_event_buffers_setup(dwc);
 		break;
 	}