linux-kernel - Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral if extcon is present"

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Message-ID: <ade865f1-8ed5-a8e3-e441-cb7688c6d001@gmail.com>
Date:   Fri, 7 Oct 2022 15:07:27 +0200
From:   Ferry Toth <fntoth@...il.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        "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"


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 :-)
>
> Thanks,
> Thinh