usb: dwc3: Set default mode for dwc_usb31

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Fri, Jul 27, 2018 at 1:14 PM, Felipe Balbi <balbi@kernel.org> wrote:

>>>>>> +
>>>>>> +               /*
>>>>>> +                * dwc_usb31 does not support OTG 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 && dwc3_is_usb31(dwc))
>>>>> shouldn't be simple
>>>>>
>>>>> else if (dwc3_is_usb31(...))
>>>>>
>>>>> ?
>>>
>>> Actually, no. We want to set the mode to peripheral _only_ when dr_mode
>>> was not specified or set to OTG. Just checking for dwc3_is_usb31(...) is
>>> not enough.
>>
>> How come?
>>
>> If I read the code correctly...
>>
>> When you go to default case in this switch it's possible if and only
>> if you have mode _exactly_ OTG. You can't have mode unknown here
>> either.
>> The check is redundant and absence of else adds additional burden on
>> the all the rest cases.
>
> Look a little closer
>
>> mode = dwc->dr_mode;
>> hw_mode = DWC3_GHWPARAMS0_MODE(dwc->hwparams.hwparams0);
>>
>> switch (hw_mode) {
>           ^^^^^^^
>           Switching on hw_mode, not mode.

Ah, indeed. That's what I have missed.
Thanks for detailed explanation!