USB: EHCI: fix handling of unusual interrupt intervals

commit 1b9a38bfa6e664ff02511314f5586d711c83cc91 upstream.

This patch (as1320) fixes two problems related to interrupt-URB
scheduling in ehci-hcd.

	URBs with an interval of 2 or 4 microframes aren't handled.
	For the time being, the patch reduces to interval to 1 uframe.

	URBs are constrained to have an interval no larger than 1024
	frames by usb_submit_urb().  But some EHCI controllers allow
	use of a schedule as short as 256 frames; for these
	controllers we may have to decrease the interval to the
	actual schedule length.

The second problem isn't very significant since few devices expose
interrupt endpoints with an interval larger than 256 frames.  But the
first problem is critical; it will prevent the kernel from working
with devices having interrupt intervals of 2 or 4 uframes.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Glynn Farrow <farrowg@sg.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 6b6c240cbe7289ae23df2e188702166deae2185d..1ae9faf1f8c26740971ba11df36af63cfe6b2e51 100644 (file)
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -802,9 +802,10 @@ qh_make (
                                 * But interval 1 scheduling is simpler, and
                                 * includes high bandwidth.
                                 */
-                               dbg ("intr period %d uframes, NYET!",
-                                               urb->interval);
-                               goto done;
+                               urb->interval = 1;
+                       } else if (qh->period > ehci->periodic_size) {
+                               qh->period = ehci->periodic_size;
+                               urb->interval = qh->period << 3;
                        }
                } else {
                        int             think_time;
@@ -827,6 +828,10 @@ qh_make (
                                        usb_calc_bus_time (urb->dev->speed,
                                        is_input, 0, max_packet (maxp)));
                        qh->period = urb->interval;
+                       if (qh->period > ehci->periodic_size) {
+                               qh->period = ehci->periodic_size;
+                               urb->interval = qh->period;
+                       }
                }
        }