linux/drivers/usb
Rene Herman 055b93c9e3 USB: ehci: stop vt6212 bus hogging
The VIA VT6212 defaults to only waiting 1us between passes over EHCI's
async ring, which hammers PCI badly ... and by preventing other devices
from accessing the bus, causes problems like drops in IDE throughput,
a problem that's been bugging users of those chips for several years.

A (partial) datasheet for this chip eventually turned up, letting us
see how to make it use a VIA-specific register to switch over to the
the normal 10us value instead, as suggested by the EHCI specification
Solution noted by Lev A. Melnikovsky.

It's not clear whether this register exists on other VIA chips; we
know that it's ineffective on the vt8235.  So this patch only applies
to chips that seem to be incarnations of the (discrete) vt6212.

Signed-off-by: Rene Herman <rene.herman@gmail.com>
Tested-by: Lev A. Melnikovsky <melnikovsky@mail.ru>
Tested-by: Alessandro Suardi <alessandro.suardi@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2008-03-24 22:26:15 -07:00
..
atm USB: Use menuconfig objects 2008-02-01 14:35:06 -08:00
class USB: fix usb open suspend race in cdc-acm 2008-02-21 15:38:49 -08:00
core USB: new quirk flag to avoid Set-Interface 2008-03-24 22:26:14 -07:00
gadget USB: fix gadgetfs class request delegation 2008-03-24 22:26:14 -07:00
host USB: ehci: stop vt6212 bus hogging 2008-03-24 22:26:15 -07:00
image USB: Drop unnecessary continue in a few drivers 2008-02-01 14:34:51 -08:00
misc USB: add new vernier product id to ldusb.c 2008-02-21 15:38:53 -08:00
mon USB: constify function pointer tables 2008-02-01 14:35:04 -08:00
serial USB: sierra: add another device id 2008-03-24 22:26:15 -07:00
storage USB: add support for Motorola ROKR Z6 cellphone in mass storage mode 2008-03-24 22:26:14 -07:00
Kconfig USB: add support for SuperH OHCI 2008-02-01 14:35:03 -08:00
Makefile USB: always visit drivers/usb/misc/ 2007-10-12 14:55:26 -07:00
README USB: fix directory references in usb/README 2007-11-28 13:58:34 -08:00
usb-skeleton.c USB: usb-skeleton leaking locks on open 2007-10-12 14:55:26 -07:00

README

To understand all the Linux-USB framework, you'll use these resources:

    * This source code.  This is necessarily an evolving work, and
      includes kerneldoc that should help you get a current overview.
      ("make pdfdocs", and then look at "usb.pdf" for host side and
      "gadget.pdf" for peripheral side.)  Also, Documentation/usb has
      more information.

    * The USB 2.0 specification (from www.usb.org), with supplements
      such as those for USB OTG and the various device classes.
      The USB specification has a good overview chapter, and USB
      peripherals conform to the widely known "Chapter 9".

    * Chip specifications for USB controllers.  Examples include
      host controllers (on PCs, servers, and more); peripheral
      controllers (in devices with Linux firmware, like printers or
      cell phones); and hard-wired peripherals like Ethernet adapters.

    * Specifications for other protocols implemented by USB peripheral
      functions.  Some are vendor-specific; others are vendor-neutral
      but just standardized outside of the www.usb.org team.

Here is a list of what each subdirectory here is, and what is contained in
them.

core/		- This is for the core USB host code, including the
		  usbfs files and the hub class driver ("khubd").

host/		- This is for USB host controller drivers.  This
		  includes UHCI, OHCI, EHCI, and others that might
		  be used with more specialized "embedded" systems.

gadget/		- This is for USB peripheral controller drivers and
		  the various gadget drivers which talk to them.


Individual USB driver directories.  A new driver should be added to the
first subdirectory in the list below that it fits into.

image/		- This is for still image drivers, like scanners or
		  digital cameras.
../input/	- This is for any driver that uses the input subsystem,
		  like keyboard, mice, touchscreens, tablets, etc.
../media/	- This is for multimedia drivers, like video cameras,
		  radios, and any other drivers that talk to the v4l
		  subsystem.
../net/		- This is for network drivers.
serial/		- This is for USB to serial drivers.
storage/	- This is for USB mass-storage drivers.
class/		- This is for all USB device drivers that do not fit
		  into any of the above categories, and work for a range
		  of USB Class specified devices. 
misc/		- This is for all USB device drivers that do not fit
		  into any of the above categories.