xref: /openbmc/u-boot/doc/README.usb (revision 15855700)
1/*
2 * (C) Copyright 2001
3 * Denis Peter, MPL AG Switzerland
4 *
5 * See file CREDITS for list of people who contributed to this
6 * project.
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of
11 * the License, or (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21 * MA 02111-1307 USA
22 *
23 */
24
25USB Support for PIP405 and MIP405 (UHCI)
26========================================
27
28The USB support is implemented on the base of the UHCI Host
29controller.
30
31Currently supported are USB Hubs, USB Keyboards and USB Floppys.
32Tested with a TEAC Floppy TEAC FD-05PUB and Chicony KU-8933 Keyboard.
33
34How it works:
35-------------
36
37The USB (at least the USB UHCI) needs a frame list (4k), transfer
38descripor and queue headers which are all located in the main memory.
39The UHCI allocates every milisecond the PCI bus and reads the current
40frame pointer. This may cause to crash the OS during boot. So the USB
41_MUST_ be stopped during OS boot. This is the reason, why the USB is
42NOT automatically started during start-up. If someone needs the USB
43he has to start it and should therefore be aware that he had to stop
44it before booting the OS.
45
46For USB keyboards this can be done by a script which is automatically
47started after the U-Boot is up and running. To boot an OS with a an
48USB keyboard another script is necessary, which first disables the
49USB and then executes the boot command. If the boot command fails,
50the script can reenable the USB kbd.
51
52Common USB Commands:
53- usb start:
54- usb reset:	    (re)starts the USB. All USB devices will be
55		    initialized and a device tree is build for them.
56- usb tree:	    shows all USB devices in a tree like display
57- usb info [dev]:   shows all USB infos of the device dev, or of all
58		    the devices
59- usb stop [f]:	    stops the USB. If f==1 the USB will also stop if
60		    an USB keyboard is assigned as stdin. The stdin
61		    is then switched to serial input.
62Storage USB Commands:
63- usb scan:	    scans the USB for storage devices.The USB must be
64		    running for this command (usb start)
65- usb device [dev]: show or set current USB staorage device
66- usb part [dev]:   print partition table of one or all USB storage
67		    devices
68- usb read addr blk# cnt:
69		    read `cnt' blocks starting at block `blk#'to
70		    memory address `addr'
71- usbboot addr dev:part:
72		    boot from USB device
73
74Config Switches:
75----------------
76CONFIG_CMD_USB	    enables basic USB support and the usb command
77CONFIG_USB_UHCI	    defines the lowlevel part.A lowlevel part must be defined
78		    if using CONFIG_CMD_USB
79CONFIG_USB_KEYBOARD enables the USB Keyboard
80CONFIG_USB_STORAGE  enables the USB storage devices
81