Date:   Mon, 10 Oct 2022 13:04:53 +0200
From:   Ferry Toth <fntoth@...il.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Felipe Balbi <balbi@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral
 if extcon is present"

Hi

On 10-10-2022 07:02, Andrey Smirnov wrote:
> On Fri, Oct 7, 2022 at 6:07 AM Ferry Toth <fntoth@...il.com> wrote:
>>
>> On 07-10-2022 04:11, Thinh Nguyen wrote:
>>> On Thu, Oct 06, 2022, Ferry Toth wrote:
>>>> Hi
>>>>
>>>> On 06-10-2022 04:12, Thinh Nguyen wrote:
>>>>> On Wed, Oct 05, 2022, Ferry Toth wrote:
>>>>>> Hi,
>>>>>>
>>>>>>        Thanks!
>>>>>>
>>>>>>        Does the failure only happen the first time host is initialized? Or can
>>>>>>        it recover after switching to device then back to host mode?
>>>>>>
>>>>>> I can switch back and forth and device mode works each time, host mode remains
>>>>>> dead.
>>>>> Ok.
>>>>>
>>>>>>        Probably the failure happens if some step(s) in dwc3_core_init() hasn't
>>>>>>        completed.
>>>>>>
>>>>>>        tusb1210 is a phy driver right? The issue is probably because we didn't
>>>>>>        initialize the phy yet. So, I suspect placing dwc3_get_extcon() after
>>>>>>        initializing the phy will probably solve the dependency problem.
>>>>>>
>>>>>>        You can try something for yourself or I can provide something to test
>>>>>>        later if you don't mind (maybe next week if it's ok).
>>>>>>
>>>>>> Yes, the code move I mentioned above "moves dwc3_get_extcon() until after
>>>>>> dwc3_core_init() but just before dwc3_core_init_mode(). AFAIU initially
>>>>>> dwc3_get_extcon() was called from within dwc3_core_init_mode() but only for
>>>>>> case USB_DR_MODE_OTG. So with this change order of events is more or less
>>>>>> unchanged" solves the issue.
>>>>>>
>>>>> I saw the experiment you did from the link you provided. We want to also
>>>>> confirm exactly which step in dwc3_core_init() was needed.
>>>> Ok. I first tried the code move suggested by Andrey (didn't work). Then
>>>> after reading the actual code I moved a bit further.
>>>>
>>>> This move was on top of -rc6 without any reverts. I did not make additional
>>>> changes to dwc3_core_init()
>>>>
>>>> So current v6.0 has: dwc3_get_extcon - dwc3_get_dr_mode - ... -
>>>> dwc3_core_init - .. - dwc3_core_init_mode (not working)
>>>>
>>>> I changed to: dwc3_get_dr_mode - dwc3_get_extcon - .. - dwc3_core_init - ..
>>>> - dwc3_core_init_mode (no change)
>>>>
>>>> Then to: dwc3_get_dr_mode - .. - dwc3_core_init - .. - dwc3_get_extcon -
>>>> dwc3_core_init_mode (works)
>>>>
>>>> .. are what I believe for this issue irrelevant calls to
>>>> dwc3_alloc_scratch_buffers, dwc3_check_params and dwc3_debugfs_init.
>>>>
>>> Right. Thanks for narrowing it down. There are still many steps in
>>> dwc3_core_init(). We have some suspicion, but we still haven't confirmed
>>> the exact cause of the failure. We can write a proper patch once we know
>>> the reason.
>> If you would like me to test your suspicion, just tell me what to do :-)
>
> OK, Ferry, I think I'm going to need clarification on specifics on
> your test setup. Can you share your kernel config, maybe your
> "/proc/config.gz", somewhere? When you say you are running vanilla
> Linux, do you mean it or do you mean vanilla tree + some patch delta?

For v6.0 I can get the exacts tonight. But earlier I had this for v5.17:

https://github.com/htot/meta-intel-edison/blob/master/meta-intel-edison-bsp/recipes-kernel/linux/linux-yocto_5.17.bb

There are 2 patches referred in #67 and #68. One is related to the 
infinite loop. The other is I believe also needed to get dwc3 to work.

All the kernel config are applied as .cfg.

Patches and cfs's here:

https://github.com/htot/meta-intel-edison/tree/master/meta-intel-edison-bsp/recipes-kernel/linux/files

> The reason I'm asking is because I'm having a hard time reproducing
> the problem on my end. In fact, when I build v6.0
> (4fe89d07dcc2804c8b562f6c7896a45643d34b2f) and then do a
>
> git revert 8bd6b8c4b100 0f0101719138 (original revert proposed by Andy)
>
> I get an infinite loop of reprobing that looks something like (some
> debug tracing, function name + line number, included):
>
> [    6.160732] tusb1210 dwc3.0.auto.ulpi: error -110 writing val 0x41
> to reg 0x80
> [    6.172299] XXXXXXXXXXX: dwc3_probe 1834
> [    6.172426] XXXXXXXXXXX: dwc3_core_init_mode 1386
> [    6.176391] XXXXXXXXXXX: dwc3_drd_init 593
> [    6.181573] dwc3 dwc3.0.auto: Driver dwc3 requests probe deferral
> [    6.191886] platform dwc3.0.auto: Added to deferred list
> [    6.197249] platform dwc3.0.auto: Retrying from deferred list
> [    6.203057] bus: 'platform': __driver_probe_device: matched device
> dwc3.0.auto with driver dwc3
> [    6.211783] bus: 'platform': really_probe: probing driver dwc3 with
> device dwc3.0.auto
> [    6.219935] XXXXXXXXXXX: dwc3_probe 1822
> [    6.219952] XXXXXXXXXXX: dwc3_core_init 1092
> [    6.223903] XXXXXXXXXXX: dwc3_core_init 1095
> [    6.234839] bus: 'ulpi': __driver_probe_device: matched device
> dwc3.0.auto.ulpi with driver tusb1210
> [    6.248335] bus: 'ulpi': really_probe: probing driver tusb1210 with
> device dwc3.0.auto.ulpi
> [    6.257039] driver: 'tusb1210': driver_bound: bound to device
> 'dwc3.0.auto.ulpi'
> [    6.264501] bus: 'ulpi': really_probe: bound device
> dwc3.0.auto.ulpi to driver tusb1210
> [    6.272553] debugfs: Directory 'dwc3.0.auto' with parent 'ulpi'
> already present!
> [    6.279978] XXXXXXXXXXX: dwc3_core_init 1099
> [    6.279991] XXXXXXXXXXX: dwc3_core_init 1103
> [    6.345769] tusb1210 dwc3.0.auto.ulpi: error -110 writing val 0x41
> to reg 0x80
> [    6.357316] XXXXXXXXXXX: dwc3_probe 1834
> [    6.357447] XXXXXXXXXXX: dwc3_core_init_mode 1386
> [    6.361402] XXXXXXXXXXX: dwc3_drd_init 593
> [    6.366589] dwc3 dwc3.0.auto: Driver dwc3 requests probe deferral
> [    6.376901] platform dwc3.0.auto: Added to deferred list
>
> which renders the system completely unusable, but USB host is
> definitely going to be broken too. Now, ironically, with my patch
> in-place, an attempt to probe extcon that ends up deferring the probe
> happens before the ULPI driver failure (which wasn't failing driver
> probe prior to https://lore.kernel.org/all/20220213130524.18748-7-hdegoede@redhat.com/),
> there no "driver binding" event that re-triggers deferred probe
> causing the loop, so the system progresses to a point where extcon is
> available and dwc3 driver eventually loads.
>
> After that, and I don't know if I'm doing the same test, USB host
> seems to work as expected. lsusb works, my USB stick enumerates as
> expected. Switching the USB mux to micro-USB and back shuts the host
> functionality down and brings it up as expected. Now I didn't try to
> load any gadgets to make sure USB gadget works 100%, but since you
> were saying it was USB host that was broken, I wasn't concerned with
> that. Am I doing the right test?
>
> For the reference what I test with is:
>   - vanilla kernel, no patch delta (sans minor debug tracing) + initrd
> built with Buildroot 2022.08.1
>   - Initrd is using systemd (don't think that really matters, but who knows)
>   - U-Boot 2022.04 (built with Buildroot as well)
>   - kernel config is x86_64_defconfig + whatever I gathered from *.cfg
> files in https://github.com/edison-fw/meta-intel-edison/tree/master/meta-intel-edison-bsp/recipes-kernel/linux/files

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