Re: [PATCH v5 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Tue, Sep 01, 2026, Marek Vasut wrote:
> On 9/1/26 3:17 AM, Thinh Nguyen wrote:
> 
> Hello Thinh,
> 
> > > > , but please drop the speed == USB_SPEED_WIRELESS check. This sanity
> > > > check is not necessary and would be flagged by dwc3 core if set anyway.
> > > Could you please point me to the code which filters the WIRELESS USB out ? I
> > > can't seem to find it in either DWC3 core or USB core, but maybe I am not
> > > looking for the right thing.
> > > 
> > > Thank you for your help !
> > 
> > You can find this in __dwc3_gadget_set_speed(). The switch statement
> > explicitly handles unsupported speeds, and setting the speed to
> > USB_SPEED_LOW or USB_SPEED_WIRELESS will trigger a complaint there.
> 
> But this is only for the gadget/peripheral mode, correct? The controller in

Yes.

> R-Car X5H is capable of both host and peripheral mode (DRD), so shouldn't
> the check be kept in here in case the controller is used in host mode ?

For host, we don't really limit based on the maximum-speed (with the
exception of 3.1 controller which allows limiting down to SuperSpeed)

> 
> Thank you for your help !
> 

We don't add sanity check for every possible user input, that's not the
pattern dwc3 drivers (or others) follow. Otherwise we'd end up with
endless redundant checks.

BR,
Thinh