Documentation/usb/ehci.rst

5 27-Dec-2002
7 The EHCI driver is used to talk to high speed USB 2.0 devices using
8 USB 2.0-capable host controller hardware.  The USB 2.0 standard is
11     - "High Speed" 480 Mbit/sec (60 MByte/sec)
12     - "Full Speed" 12 Mbit/sec (1.5 MByte/sec)
13     - "Low Speed" 1.5 Mbit/sec
15 USB 1.1 only addressed full speed and low speed.  High speed devices
24 high speed "split transactions" that don't waste transfer bandwidth.
31 While usb-storage devices have been available since mid-2001 (working
33 been available since late 2001, and other kinds of high speed devices
34 appear to be on hold until more systems come with USB 2.0 built-in.
39 other changes to the Linux-USB core APIs, including the hub driver,
43 - David Brownell
56 --------------
62 High Speed Isochronous (ISO) transfer support is also functional, but
67 transfers can't share much code with the code for high speed ISO transfers,
69 most USB audio and video devices can't be connected to high speed buses.
72 ---------------
99     # modprobe ehci-hcd
103     # rmmod ehci-hcd
106 "ohci-hcd"  or "uhci-hcd".  In case of any trouble with the EHCI driver,
127 		usb-storage doing disk I/O; watch the request queues!)
138 but they may want to check for "usb_device->speed == USB_SPEED_HIGH".
139 High speed devices can do things that full speed (or low speed) ones
140 can't, such as "high bandwidth" periodic (interrupt or ISO) transfers.
142 periodic transfers) use different encodings when operating at high speed.
150 Performance  chapter
157 individual high speed packets, driver intelligence, and of course the
158 overall system load.  Latency is also a performance concern.
170 Hardware Performance
171 --------------------
194 default ehci-hcd driver uses the minimum latency, which means that if
198 Software Performance
199 --------------------
201 To get even 20 MByte/sec transfer rates, Linux-USB device drivers will
204 When drivers don't do that, their performance results will show it.
220 help make high speed transfers run as fast as they can.
224    Interrupt and ISO transfer performance issues.  Those periodic
226    to trigger "high bandwidth" modes.