On Tue, 31 Oct 2017, Roger Quadros wrote:
> Currently 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 than that supported by the
> UDC controller driver.
>
> Select the lesser of the 2 speeds so both UDC and gadget function
> driver are operating within limits.
>
> This fixes PHY Erratic errors and 2 second enumeration delay on
> TI's AM437x platforms.
>
> Fixes: 6099eca796ae ("usb: gadget: core: introduce ->udc_set_speed() method")
> Cc: <sta...@vger.kernel.org> # v4.13+
> Reported-by: Dylan Howey <dylan.ho...@tennantco.com>
> Signed-off-by: Roger Quadros <rog...@ti.com>
> ---
> v2:
> - Move speed limiting code to UDC core.
>
> drivers/usb/gadget/udc/core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index d41d07a..def1b05 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -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);
> + }
> }
>
> /**
Roger, would you like to send in a follow-up patch that removes the now
unnecessary code from dummy_udc_set_speed() in dummy_hcd.c?
Alan Stern
