linux-kernel - Re: [PATCH v4] usb: dwc3: Don't switch OTG -> peripheral if extcon is present

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Message-ID: <47a0249c-e129-7e98-503d-4254f216e485@gmail.com>
Date:   Fri, 23 Sep 2022 23:12:28 +0200
From:   Ferry Toth <fntoth@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Andrey Smirnov <andrew.smirnov@...il.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

Hi,

Op 23-09-2022 om 18:42 schreef Andy Shevchenko:
> 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.
>
>>> 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.
>
> 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?

On v6.0-rc6 and reverting manually only this line

- if (mode == USB_DR_MODE_OTG && !dwc->edev &&

+ if (mode == USB_DR_MODE_OTG &&

host mode still does not work (no change visible).

>
>>   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?
> It is not always possible to have an extcon driver available, that's why in
> some cases the probe of it defers. I dunno how your patch supposed to work
> in that case.
>
>> Does tracing the "mrfld_bcove_pwrsrc" driver (the
>> excton provider in this case AFIACT) show anything interesting?
> I believe there is nothing interesting.
>