On Mon, 15 Sep 2014, Mathias Nyman wrote:
> I haven't had time to dig into the usbmon traces, but I just got another report from Gunter K�gsmann about similar scanner problem, and I just noticed
> that in both cases we round the interval for high speed bulk _IN_ endpoint, which should not have interval set at all.
> The interval value should be ignored by host, but maybe setting it still could cause some issues.
>
> I don't have high hopes for this patch, but it's worth a shot.
> Can you try this out and see if it makes any difference?
>
> -Mathias
>
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 8936211..7f21b77 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -1291,7 +1291,8 @@ static unsigned int xhci_get_endpoint_interval(struct usb_device *udev,
> /* Max NAK rate */
> if (usb_endpoint_xfer_control(&ep->desc) ||
> usb_endpoint_xfer_bulk(&ep->desc)) {
> - interval = xhci_parse_microframe_interval(udev, ep);
> + if (!usb_endpoint_dir_in(&ep->desc))
> + interval = xhci_parse_microframe_interval(udev, ep);
It's not a good idea to test the direction of control endpoints, since
they are bi-directional.
Also, xhci_parse_microframe_interval assumes the value is stored with
an exponential encoding, but the NAK rate value for control and
bulk-OUT endpoints is stored in the endpoint descriptor directly as a
number of microframes (not exponential).
It's not fully clear how xHCI controllers use the Interval field in the
Endpoint Context. Table 65 notably fails to include a line for HS
bulk-OUT/control endpoints, and the text isn't clear as to whether the
field is interpreted using exponential coding for non-periodic
endpoints. As near as I can tell, it is -- which means you should call
xhci_microframes_to_exponent() here, not
xhci_parse_microframe_interval().
Alan Stern
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