diff options
authorMathias Nyman <>2015-04-30 17:16:03 +0300
committerGreg Kroah-Hartman <>2015-06-06 08:19:34 -0700
commit697409c7b1b1c9cdfd3997452ea9a601bae5d06e (patch)
parenta5bfa46306df0fc1b4ef5ec23d720caeacde6b1e (diff)
xhci: Solve full event ring by increasing TRBS_PER_SEGMENT to 256
commit 18cc2f4cbbaf825a4fedcf2d60fd388d291e0a38 upstream. Our event ring consists of only one segment, and we risk filling the event ring in case we get isoc transfers with short intervals such as webcams that fill a TD every microframe (125us) With 64 TRB segment size one usb camera could fill the event ring in 8ms. A setup with several cameras and other devices can fill up the event ring as it is shared between all devices. This has occurred when uvcvideo queues 5 * 32TD URBs which then get cancelled when the video mode changes. The cancelled URBs are returned in the xhci interrupt context and blocks the interrupt handler from handling the new events. A full event ring will block xhci from scheduling traffic and affect all devices conneted to the xhci, will see errors such as Missed Service Intervals for isoc devices, and and Split transaction errors for LS/FS interrupt devices. Increasing the TRB_PER_SEGMENT will also increase the default endpoint ring size, which is welcome as for most isoc transfer we had to dynamically expand the endpoint ring anyway to be able to queue the 5 * 32TDs uvcvideo queues. The default size used to be 64 TRBs per segment Signed-off-by: Mathias Nyman <> Signed-off-by: Greg Kroah-Hartman <>
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 7225dd242bfa..70facb725105 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1268,7 +1268,7 @@ union xhci_trb {
* since the command ring is 64-byte aligned.
* It must also be greater than 16.
-#define TRBS_PER_SEGMENT 64
+#define TRBS_PER_SEGMENT 256
/* Allow two commands + a link TRB, along with any reserved command TRBs */