Commit dfa49c4a authored by Dmitry Torokhov's avatar Dmitry Torokhov Committed by Sarah Sharp
Browse files

USB: xhci - fix math in xhci_get_endpoint_interval() 



When parsing exponent-expressed intervals we subtract 1 from the
value and then expect it to match with original + 1, which is
highly unlikely, and we end with frequent spew:

	usb 3-4: ep 0x83 - rounding interval to 512 microframes

Also, parsing interval for fullspeed isochronous endpoints was
incorrect - according to USB spec they use exponent-based
intervals (but xHCI spec claims frame-based intervals). I trust
USB spec more, especially since USB core agrees with it.

This should be queued for stable kernels back to 2.6.31.

Reviewed-by: default avatarMicah Elizabeth Scott <micah@vmware.com>
Signed-off-by: default avatarDmitry Torokhov <dtor@vmware.com>
Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org
parent 926008c9

drivers/usb/host/xhci-mem.c

+62 −28
Original line number Diff line number Diff line
@@ -974,6 +974,47 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud 
	return 0;

}



/*

 * Convert interval expressed as 2^(bInterval - 1) == interval into

 * straight exponent value 2^n == interval.

 *

 */

static unsigned int xhci_parse_exponent_interval(struct usb_device *udev,

		struct usb_host_endpoint *ep)

{

	unsigned int interval;



	interval = clamp_val(ep->desc.bInterval, 1, 16) - 1;

	if (interval != ep->desc.bInterval - 1)

		dev_warn(&udev->dev,

			 "ep %#x - rounding interval to %d microframes\n",

			 ep->desc.bEndpointAddress,

			 1 << interval);



	return interval;

}



/*

 * Convert bInterval expressed in frames (in 1-255 range) to exponent of

 * microframes, rounded down to nearest power of 2.

 */

static unsigned int xhci_parse_frame_interval(struct usb_device *udev,

		struct usb_host_endpoint *ep)

{

	unsigned int interval;



	interval = fls(8 * ep->desc.bInterval) - 1;

	interval = clamp_val(interval, 3, 10);

	if ((1 << interval) != 8 * ep->desc.bInterval)

		dev_warn(&udev->dev,

			 "ep %#x - rounding interval to %d microframes, ep desc says %d microframes\n",

			 ep->desc.bEndpointAddress,

			 1 << interval,

			 8 * ep->desc.bInterval);



	return interval;

}



/* Return the polling or NAK interval.

 *

 * The polling interval is expressed in "microframes".  If xHCI's Interval field
@@ -991,45 +1032,38 @@ static unsigned int xhci_get_endpoint_interval(struct usb_device *udev, 
	case USB_SPEED_HIGH:

		/* Max NAK rate */

		if (usb_endpoint_xfer_control(&ep->desc) ||

				usb_endpoint_xfer_bulk(&ep->desc))

		    usb_endpoint_xfer_bulk(&ep->desc)) {

			interval = ep->desc.bInterval;

			break;

		}

		/* Fall through - SS and HS isoc/int have same decoding */



	case USB_SPEED_SUPER:

		if (usb_endpoint_xfer_int(&ep->desc) ||

		    usb_endpoint_xfer_isoc(&ep->desc)) {

			if (ep->desc.bInterval == 0)

				interval = 0;

			else

				interval = ep->desc.bInterval - 1;

			if (interval > 15)

				interval = 15;

			if (interval != ep->desc.bInterval + 1)

				dev_warn(&udev->dev, "ep %#x - rounding interval to %d microframes\n",

						ep->desc.bEndpointAddress, 1 << interval);

			interval = xhci_parse_exponent_interval(udev, ep);

		}

		break;

	/* Convert bInterval (in 1-255 frames) to microframes and round down to

	 * nearest power of 2.

	 */



	case USB_SPEED_FULL:

		if (usb_endpoint_xfer_int(&ep->desc)) {

			interval = xhci_parse_exponent_interval(udev, ep);

			break;

		}

		/*

		 * Fall through for isochronous endpoint interval decoding

		 * since it uses the same rules as low speed interrupt

		 * endpoints.

		 */



	case USB_SPEED_LOW:

		if (usb_endpoint_xfer_int(&ep->desc) ||

		    usb_endpoint_xfer_isoc(&ep->desc)) {

			interval = fls(8*ep->desc.bInterval) - 1;

			if (interval > 10)

				interval = 10;

			if (interval < 3)

				interval = 3;

			if ((1 << interval) != 8*ep->desc.bInterval)

				dev_warn(&udev->dev,

						"ep %#x - rounding interval"

						" to %d microframes, "

						"ep desc says %d microframes\n",

						ep->desc.bEndpointAddress,

						1 << interval,

						8*ep->desc.bInterval);



			interval = xhci_parse_frame_interval(udev, ep);

		}

		break;



	default:

		BUG();

	}

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