Roger Quadros <rogerq@ti.com> writes:

> UDC core calls .udc_set_speed() with the speed parameter
> containing the maximum speed supported by the gadget function
> driver. This might very well be more or less than that
> supported by the dwc3 controller driver.
>
> Select the lesser of the 2 speeds so both are operating
> within limits.
>
> This fixes PHY Erratic errors and 2 second enumeration delay on
> TI's AM437x platforms.
>
> Fixes: 7d8d0639565f ("usb: dwc3: gadget: implement ->udc_set_speed()")
> Cc: <stable@vger.kernel.org> # v4.13+
> Reported-by: Dylan Howey <Dylan.Howey@tennantco.com>
> Signed-off-by: Roger Quadros <rogerq@ti.com>
> ---
>  drivers/usb/dwc3/gadget.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index f064f15..9f27ec0 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2008,6 +2008,8 @@ static void dwc3_gadget_set_speed(struct usb_gadget *g,
>  	unsigned long		flags;
>  	u32			reg;
>  
> +	speed = min(g->max_speed, speed);

should we do that in udc core itself?

@@ -1080,8 +1080,12 @@ static inline void usb_gadget_udc_stop(struct usb_udc *udc)
 static inline void usb_gadget_udc_set_speed(struct usb_udc *udc,
 					    enum usb_device_speed speed)
 {
-	if (udc->gadget->ops->udc_set_speed)
-		udc->gadget->ops->udc_set_speed(udc->gadget, speed);
+	if (udc->gadget->ops->udc_set_speed) {
+		enum usb_device_speed s;
+
+		s = min(speed, udc->gadget->max_speed);
+		udc->gadget->ops->udc_set_speed(udc->gadget, s);
+	}
 }
 
 /**

then the fix applies for all UDCs.

-- 
balbi