Merge branch 'perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux...

[pandora-kernel.git] / Documentation / ABI / testing / sysfs-module

diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module
index cfcec3b..9489ea8 100644 (file)
--- 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.