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

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Date:   Fri, 23 Sep 2022 19:42:40 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     Ferry Toth <fntoth@...il.com>,
        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 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?

>  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.

-- 
With Best Regards,
Andy Shevchenko