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

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Date:   Thu, 6 Oct 2022 14:28:28 +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"

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.

>
> Thanks,
> Thinh