1 files changed, 23 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module
index cfcec3bffc0a..9489ea8e294c 100644
--- a/Documentation/ABI/testing/sysfs-module
+++ b/Documentation/ABI/testing/sysfs-module
@@ -10,3 +10,26 @@ KernelVersion:	2.6.35
 Contact:        masa-korg@dsn.okisemi.com
 Description:    Write/read Option ROM data.
 
+
+What:           /sys/module/ehci_hcd/drivers/.../uframe_periodic_max
+Date:           July 2011
+KernelVersion:  3.1
+Contact:        Kirill Smelkov <kirr@mns.spb.ru>
+Description:    Maximum time allowed for periodic transfers per microframe (μs)
+
+                [ USB 2.0 sets maximum allowed time for periodic transfers per
+                  microframe to be 80%, that is 100 microseconds out of 125
+                  microseconds (full microframe).
+
+                  However there are cases, when 80% max isochronous bandwidth is
+                  too limiting. For example two video streams could require 110
+                  microseconds of isochronous bandwidth per microframe to work
+                  together. ]
+
+                Through this setting it is possible to raise the limit so that
+                the host controller would allow allocating more than 100
+                microseconds of periodic bandwidth per microframe.
+
+                Beware, non-standard modes are usually not thoroughly tested by
+                hardware designers, and the hardware can malfunction when this
+                setting differ from default 100.