Re: [PATCH] usb: dwc3: omap: Fix imprecise external abort and oops on boot

[Felipe Balbi <balbi-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

Hi,

Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> writes:
> * Felipe Balbi <balbi-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> [161208 01:45]:
>> 
>> Hi,
>> 
>> Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> writes:
>> > Somehow starting with v4.9-rc7 there have been imprecise
>> 
>> There's nothing touching dwc3 since v4.9-rc5.
>
> Right, nothing obvious has changed. I think it's just a slight timing
> change in the code that started triggering it.

could be

>> > external aborts on omap5-uevm dwc3 controller. I have not been
>> > able to bisect what exactly triggered this as it does not always
>> > happen. It seems that something changed with probing that
>> > now exposes the issue:
>> >
>> > Unhandled fault: imprecise external abort (0x1406) at 0x00000000
>> 
>> hmmm, clock disabled... dwc3-omap shouldn't have pm runtime at all.
>
> It does for the interconnect target module clkctrl register via PM
> runtime. That's the "usb_otg_ss" module.

but that's all hidden in omap_device.c, we don't touch it from driver
perspective.

>> > ...
>> > PC is at dwc3_omap_interrupt_thread+0x20/0x80
>> > LR is at irq_thread_fn+0x1c/0x54
>> > ...
>> > [<c0989fa8>] (dwc3_omap_interrupt_thread) from [<c038a4d8>]
>> > (irq_thread_fn+0x1c/0x54)
>> > [<c038a4d8>] (irq_thread_fn) from [<c038a7b0>] (irq_thread+0x12c/0x1f0)
>> > [<c038a7b0>] (irq_thread) from [<c035d6f0>] (kthread+0xdc/0xf4)
>> > [<c035d6f0>] (kthread) from [<c0307d78>] (ret_from_fork+0x14/0x3c)
>> > ...
>> >
>> > Unable to handle kernel paging request at virtual address ffffffec
>> > ...
>> > Internal error: Oops: 37 [#2] SMP ARM
>> > PC is at kthread_data+0x4/0xc
>> > LR is at irq_thread_dtor+0x28/0xd0
>> > ...
>> > [<c035e0b4>] (kthread_data) from [<c038a5dc>] (irq_thread_dtor+0x28/0xd0)
>> > [<c038a5dc>] (irq_thread_dtor) from [<c035bef0>] (task_work_run+0xb8/0xdc)
>> > [<c035bef0>] (task_work_run) from [<c03448d4>] (do_exit+0x314/0xa20)
>> > [<c03448d4>] (do_exit) from [<c030bea8>] (die+0x410/0x474)
>> > [<c030bea8>] (die) from [<c0301350>] (do_DataAbort+0xb4/0xb8)
>> > [<c0301350>] (do_DataAbort) from [<c030c578>] (__dabt_svc+0x58/0x80)
>> > Exception stack(0xee777ec8 to 0xee777f10)
>> > 7ec0:                   0000014d ee6e6f10 00000034 fc020034 ee6e6f10 ee1eec00
>> > 7ee0: 00000000 00000000 ee6ec640 c038a4bc 00000000 00000000 00000000 ee777f18
>> > 7f00: c038a4d8 c0989fa8 60000013 ffffffff
>> > [<c030c578>] (__dabt_svc) from [<c0989fa8>] (dwc3_omap_interrupt_thread+0x20/0x80)
>> > [<c0989fa8>] (dwc3_omap_interrupt_thread) from [<c038a4d8>] (irq_thread_fn+0x1c/0x54)
>> > [<c038a4d8>] (irq_thread_fn) from [<c038a7b0>] (irq_thread+0x12c/0x1f0)
>> > [<c038a7b0>] (irq_thread) from [<c035d6f0>] (kthread+0xdc/0xf4)
>> > [<c035d6f0>] (kthread) from [<c0307d78>] (ret_from_fork+0x14/0x3c)
>> >
>> > Fix the issue by making sure the dwc3 interrupts are disabled
>> > before we call devm_request_threaded_irq().
>> 
>> that should already be the case. Are you sure that register isn't zero
>> in probe?
>
> Looks like irq0_status = 0 and irqmisc_status = 0x2121. Also just
> clearing irqmisc with dwc3_omap_write_irqmisc_clr(omap, 0xffffffff)
> stops the issue from happening.
>
> There is some deferred probing happening but irqmisc is always 0x2121.

some spurious irq status from ROM code, perhaps? Are you not resetting
usb_otg_ss hwmod? We shouldn't have any pending interrupts when we get
to probe(), if we do have them, then we need an erratum for it.

You could try making usb_otg_ss is reset by hwmod. It would also be good
to check other OMAP-ish devices sporting dwc3 (DRA7x, AM437x, AM57x) if
they have the same behavior.

Adding Nishanth to the loop too for reference.

-- 
balbi
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