Re: [PATCH v6] usb: common: add API to set usb otg capabilities by device tree

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 06/23/2015 05:56 AM, Roger Quadros wrote:
> + Kukjin, Stephen,
>
> for board specific USB question.
>
> On Tue, 23 Jun 2015 16:35:49 +0800
> Li Jun <b47624-KZfg59tc24xl57MIdRCFDg@public.gmane.org> wrote:
>
>> On Tue, Jun 23, 2015 at 10:43:28AM +0300, Roger Quadros wrote:
>>>>>
>>>>> If the dr_mode was "otg" for such case and we want OTG disabled then it is really the DT fault.
>>>>
>>>> It's ID pin detect for dual role switch as many current OTG controllers have.
>>>> not DT fault, its dt only has a dr_mode = "otg".
>>>>
>>>>> We don't need to tackle this case. Just fix up the DT to dr_mode = "peripheral" if
>>>>> OTG behaviour is not needed.
>>>>>
>>>> OTG behaviour is not needed, so we need disable HNP/SRP/ADP. but dr_mode =
>>>> "otg" as it already works fine with ID pin detect.
>>>
>>> Do you know which platform has plain non-otg dual-role working as of today
>>> with dr_mode set to "otg"?
>>
>> I don't know.
>> The dt property dr_mode is already there, and currently there are some platforms
>> as its user, so I assume those platforms either are non-otg dual-role, or real OTG
>> with HNP supported, I guess most are the former cases; chipidea is the later case.
>>
>>> For TI platforms none of them have it working currently.
>>>
>> So for Ti platforms, some enables non-otg dual-role function but do not use
>> dr_mode = "otg"?
>
> for TI we have only musb based and dwc3 based platforms. MUSB based are OTG.
> dwc3 doesn't support dual-role or OTG yet so we use either "peripheral" or "Host"
>
>>
>> For those only have non-otg dual-role platforms, no matter using dr_mode or not,
>> we need keep it's real OTG disabled for legacy users after it's controller
>> driver adds real OTG later.
>
> I wouldn't even bother about platforms expecting dual-role behaviour
> with dr_mode not set to "otg". That is just plain wrong and can't be supported.
>
> These are the dts files having dr_mode == "otg".
> I've sorted them as per Soc vendor and USB controller
...
> Nvidia
> ------
> arm/boot/dts/tegra20-seaboard.dts:		dr_mode = "otg";
> 	compatible = "nvidia,tegra20-ehci", "usb-ehci";
> arm/boot/dts/tegra30-colibri-eval-v3.dts:		dr_mode = "otg";
> 	compatible = "nvidia,tegra30-ehci", "usb-ehci";
>
> I couldn't find gadget side implementation for this.
> Stephen, any comments on whether this board supports true OTG operation or just dual-role operation?

Sorry for the slow reply; I was on vacation.

I'm not sure what the difference is?

I won't be able to answer for the Colibri board since I'm not familiar 
with the HW. I have the schematics for Seaboard, so I should be able to 
answer once I understand the question:-)
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