diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-module | 23 | ||||
| -rw-r--r-- | Documentation/usb/ehci.txt | 2 |
2 files changed, 25 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. diff --git a/Documentation/usb/ehci.txt b/Documentation/usb/ehci.txt index 9dcafa7d930d..160bd6c3ab7b 100644 --- a/Documentation/usb/ehci.txt +++ b/Documentation/usb/ehci.txt @@ -210,3 +210,5 @@ TBD: Interrupt and ISO transfer performance issues. Those periodic transfers are fully scheduled, so the main issue is likely to be how to trigger "high bandwidth" modes. +TBD: More than standard 80% periodic bandwidth allocation is possible +through sysfs uframe_periodic_max parameter. Describe that. |