[PATCH] usb: cdns3: fix cdns3_bind() to avoid returning error and probe parent

[Siddharth Vadapalli]

On 03/03/26 19:37, Marek Vasut wrote:
> On 3/1/26 6:25 AM, Siddharth Vadapalli wrote:
> 
>>>> There are two users of cdns3_bind() which have registered their 
>>>> own .bind() callback as cdns3_bind():
>>>> 1. cdns3-starfive.c driver
>>>> 2. cdns3-ti.c driver
>>>> Since .bind() is called before .probe()
>>>
>>> .bind callback is meant to BIND the driver instance (to a DT node), it 
>>> is not meant to initialize the hardware. .probe callback is meant to 
>>
>> I agree. But that's exactly where the issue lies. When 'dr_mode' is set 
>> to OTG, cdns3_bind() is unable to determine if the driver to bind to the 
>> DT node is "cdns-usb3-host" or "cdns-usb3-peripheral".
>>
>> Since [0], we attempt to identify if OTG should imply 'peripheral' or 
>> 'host'. But to do that, [0] needs to read the VBUS Valid field of the OTG 
>> Status register. And register access requires the USB Controller to be 
>> powered ON.
> 
> Correct, so bind is the wrong place to do any HW access .
> 
>> [0]: bfb530e06ca6 ("usb: cdns3: use VBUS Valid to determine role for 
>> dr_mode OTG")
>>
>>> initialize the hardware. This is fundamental part of the U-Boot DM lazy 
>>> initialization scheme. If something does initialize hardware in .bind, 
>>> then it is very likely wrong.
>>>
>>>> , and, since cdns3_bind() is also the .bind() callback of the above 
>>>> drivers, device_probe() has to be added here itself. Moreover, it is 
>>>> only due to the register accesses being performed by the recently 
>>>> introduced cdns3_get_otg_mode() function that we need the USB 
>>>> Controller to be powered ON at this stage.
>>> So, can we fix this so the HW initialization won't be happening in bind, 
>>> but instead in .probe ?
>>
>> That isn't possible
> 
> Can you investigate how to make that possible ? Maybe by having some 
> common .probe implementation that would determine the OTG state, or by 
> having some stub driver which handles the OTG selection ?
A common .probe will not work because the .id has to be either
UCLASS_USB_GADGET_GENERIC OR UCLASS_USB
for the new stub driver (say cdns-usb3-otg). By fixing .id beforehand, we 
will always fail to probe the driver for the case where the desired role is 
the opposite of the role corresponding to .id.