Message-Id: <5748396a-fe0b-413c-b8ac-d24d959091bc@app.fastmail.com>
Date:   Mon, 26 Sep 2022 12:45:17 +0200
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Ferry Toth" <fntoth@...il.com>,
        "Andrey Smirnov" <andrew.smirnov@...il.com>,
        "Andy Shevchenko" <andriy.shevchenko@...el.com>
Cc:     "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Felipe Balbi" <balbi@...nel.org>,
        "Thinh Nguyen" <thinhn@...opsys.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Thinh Nguyen" <Thinh.Nguyen@...opsys.com>
Subject: Re: [PATCH v4] usb: dwc3: Don't switch OTG -> peripheral if extcon is present



On Sun, Sep 25, 2022, at 21:21, Ferry Toth wrote:
> Hi,
>
> Promising results below.
>
> Op 24-09-2022 om 23:29 schreef Ferry Toth:
>> Hi,
>>
>> One more test
>>
>> Op 23-09-2022 om 20:23 schreef Andrey Smirnov:
>>> On Fri, Sep 23, 2022 at 9:42 AM Andy Shevchenko
>>> <andriy.shevchenko@...el.com> wrote:
>>>> On Thu, Sep 22, 2022 at 04:32:55PM -0700, Andrey Smirnov wrote:
>>>>> On Thu, Sep 22, 2022 at 3:23 AM Ferry Toth <fntoth@...il.com> wrote:
>>>>>> On 22-09-2022 12:08, Andy Shevchenko wrote:
>>>>>> On Sun, Apr 03, 2022 at 09:49:07AM -0700, Andrey Smirnov wrote:
>>>> FYI: For now I sent a revert, but if we got a solution quicker we 
>>>> always
>>>> can choose the course of actions.
>>>>
>>> I think we have another problem. This patch happened in parallel to mine
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.0-rc6&id=ab7aa2866d295438dc60522f85c5421c6b4f1507 
>>>
>>>
>>> so my changes didn't have that fix in mind and I think your revert
>>> will not preserve that fix. Can you update your revert to take care of
>>> that too, please?
>>>
>>> I'm really confused how the above commit could be followed up by:
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/usb/dwc3/drd.c?h=v6.0-rc6&id=0f01017191384e3962fa31520a9fd9846c3d352f 
>>>
>>>
>>> the diffs in dwc3_drd_init seem contradictory
>>>
>>>>>> If the extcon device exists, get the mode from the extcon device. If
>>>>>> the controller is DRD and the driver is unable to determine the mode,
>>>>>> only then default the dr_mode to USB_DR_MODE_PERIPHERAL.
>>>>>>
>>>>>> According to Ferry (Cc'ed) this broke Intel Merrifield platform. 
>>>>>> Ferry, can you
>>>>>> share bisect log?
>>>>>>
>>>>>> I can but not right now. But what I did was bisect between 5.18.0 
>>>>>> (good) and 5.19.0 (bad) then when I got near the culprit (~20 
>>>>>> remaining) based on the commit message I tried 
>>>>>> 0f01017191384e3962fa31520a9fd9846c3d352f "usb: dwc3: Don't switch 
>>>>>> OTG -> peripheral if extcon is present" (bad) and commit before 
>>>>>> that (good).
>>>>>>
>>>>>> The effect of the patch is that on Merrifield (I tested with Intel 
>>>>>> Edison Arduino board which has a HW switch to select between host 
>>>>>> and device mode) device mode works but in host mode USB is 
>>>>>> completely not working.
>>>>>>
>>>>>> Currently on host mode - when working - superfluous error messages 
>>>>>> from tusb1210 appear. When host mode is not working there are no 
>>>>>> tusb1210 messages in the logs / on the console at all. Seemingly 
>>>>>> tusb1210 is not probed, which points in the direction of a 
>>>>>> relation to extcon.
>>>>>>
>>>>>> Taking into account the late cycle, I would like to revert the 
>>>>>> change. And
>>>>>> Ferry and I would help to test any other (non-regressive) approach).
>>>>>>
>>>>>> I have not yet tested if a simple revert fixes the problem but 
>>>>>> will tonight.
>>>>>>
>>>>>>
>>>>>> I would be happy to test other approaches too.
>>>>>
>>>>> It's a bit hard for me to suggest an alternative approach without
>>>>> knowing how things are breaking in this case. I'd love to order one of
>>>>> those boards to repro and fix this on my end, but it looks like this
>>>>> HW is EOLed and out of stock in most places. If you guys know how to
>>>>> get my hands on those boards I'm all ears.
>>>> There are still some second hand Intel Edison boards flying around
>>>> (but maybe cost a bit more than expected) and there are also
>>>> Dell Venue 7 3740 tablets based on the same platform/SoC. The latter
>>>> option though requires more actions in order something to be boot
>>>> there.
>>>>
>>> OK, I'll check e-bay just in case.
>>>
>>>> In any case, it's probably quicker to ask Ferry or me for testing.
>>>> (Although currently I have no access to the board to test OTG, it's
>>>>   remote device which I can only power on and off and it has always
>>>>   be in host mode.)
>>>>
>>>>> Barring that, Ferry can you dig more into this failure? E.g. is it 
>>>>> this hunk
>>>>>
>>>>> @@ -85,7 +86,7 @@ static int dwc3_get_dr_mode(struct dwc3 *dwc)
>>>>>                   * mode. If the controller supports DRD but the 
>>>>> dr_mode is not
>>>>>                   * specified or set to OTG, then set the mode to 
>>>>> peripheral.
>>>>>                   */
>>>>> -               if (mode == USB_DR_MODE_OTG &&
>>>>> +               if (mode == USB_DR_MODE_OTG && !dwc->edev &&
>>>>>                      (!IS_ENABLED(CONFIG_USB_ROLE_SWITCH) ||
>>>>> !device_property_read_bool(dwc->dev, "usb-role-switch")) &&
>>>>>                      !DWC3_VER_IS_PRIOR(DWC3, 330A))
>>>>> @@ -1632,6 +1633,51 @@ static void dwc3_check_params(struct dwc3 *dwc)
>>>>>          }
>>>>>   }
>>>>>
>>>>> that's problematic or moving
>>>> I think you wanted to revert only this line and test?
>>> Yes.
>>>
>>>>>   static int dwc3_probe(struct platform_device *pdev)
>>>>>   {
>>>>>          struct device           *dev = &pdev->dev;
>>>>> @@ -1744,6 +1790,13 @@ static int dwc3_probe(struct platform_device 
>>>>> *pdev)
>>>>>                  goto err2;
>>>>>          }
>>>>>
>>>>> +       dwc->edev = dwc3_get_extcon(dwc);
>>>>> +       if (IS_ERR(dwc->edev)) {
>>>>> +               ret = PTR_ERR(dwc->edev);
>>>>> +               dev_err_probe(dwc->dev, ret, "failed to get 
>>>>> extcon\n");
>>>>> +               goto err3;
>>>>> +       }
>>>>> +
>>>>>          ret = dwc3_get_dr_mode(dwc);
>>>>>          if (ret)
>>>>>                  goto err3;
>>>>>
>>>>> to happen earlier?
>>
>> I tried moving dwc3_get_extcon after dwc3_get_dr_mode like so::
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 8c8e32651473..3bf370def546 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -1843,6 +1843,10 @@ static int dwc3_probe(struct platform_device 
>> *pdev)
>>          goto err2;
>>      }
>>
>> +    ret = dwc3_get_dr_mode(dwc);
>> +    if (ret)
>> +        goto err3;
>> +
>>      dwc->edev = dwc3_get_extcon(dwc);
>>      if (IS_ERR(dwc->edev)) {
>>          ret = PTR_ERR(dwc->edev);
>> @@ -1850,10 +1854,6 @@ static int dwc3_probe(struct platform_device 
>> *pdev)
>>          goto err3;
>>      }
>>
>> -    ret = dwc3_get_dr_mode(dwc);
>> -    if (ret)
>> -        goto err3;
>> -
>>      ret = dwc3_alloc_scratch_buffers(dwc);
>>      if (ret)
>>          goto err3;
>
> After trying to understand the code a bit, I successfully tested the 
> following move:
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 8c8e32651473..4a38cff8cb16 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1843,13 +1843,6 @@ static int dwc3_probe(struct platform_device *pdev)
>           goto err2;
>       }
>
> -    dwc->edev = dwc3_get_extcon(dwc);
> -    if (IS_ERR(dwc->edev)) {
> -        ret = PTR_ERR(dwc->edev);
> -        dev_err_probe(dwc->dev, ret, "failed to get extcon\n");
> -        goto err3;
> -    }
> -
>       ret = dwc3_get_dr_mode(dwc);
>       if (ret)
>           goto err3;
> @@ -1867,6 +1860,13 @@ static int dwc3_probe(struct platform_device *pdev)
>       dwc3_check_params(dwc);
>       dwc3_debugfs_init(dwc);
>
> +    dwc->edev = dwc3_get_extcon(dwc);
> +    if (IS_ERR(dwc->edev)) {
> +        ret = PTR_ERR(dwc->edev);
> +        dev_err_probe(dwc->dev, ret, "failed to get extcon\n");
> +        goto err5;
> +    }
> +
>       ret = dwc3_core_init_mode(dwc);
>       if (ret)
>           goto err5;
>
> This 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.
>
> Due to move I modified goto to err5, not sure if that is correct.

err5 is correct there, that failure path starts to clean up what dwc3_core_init did.

>
> Thoughts? Can we get something like this in quick or should we revert first?

I don't know anything about that platform and following this thread is a bit hard
for me since I lack context so this is a total guess: dwc3_core_init brings up the
PHYs and also soft resets the core. Could any of these two things interact with your
extcon and somehow break it?


Sven

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