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

[Marek Vasut]

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 ?