u-boot/doc/README.usb

/*
 * (C) Copyright 2001
 * Denis Peter, MPL AG Switzerland
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

USB Support
===========

The USB support is implemented on the base of the UHCI Host
controller.

Currently supported are USB Hubs, USB Keyboards, USB Floppys, USB
flash sticks and USB network adaptors.
Tested with a TEAC Floppy TEAC FD-05PUB and Chicony KU-8933 Keyboard.

How it works:
-------------

The USB (at least the USB UHCI) needs a frame list (4k), transfer
descripor and queue headers which are all located in the main memory.
The UHCI allocates every milisecond the PCI bus and reads the current
frame pointer. This may cause to crash the OS during boot. So the USB
_MUST_ be stopped during OS boot. This is the reason, why the USB is
NOT automatically started during start-up. If someone needs the USB
he has to start it and should therefore be aware that he had to stop
it before booting the OS.

For USB keyboards this can be done by a script which is automatically
started after the U-Boot is up and running. To boot an OS with a an
USB keyboard another script is necessary, which first disables the
USB and then executes the boot command. If the boot command fails,
the script can reenable the USB kbd.

Common USB Commands:
- usb start:
- usb reset:	    (re)starts the USB. All USB devices will be
		    initialized and a device tree is build for them.
- usb tree:	    shows all USB devices in a tree like display
- usb info [dev]:   shows all USB infos of the device dev, or of all
		    the devices
- usb stop [f]:	    stops the USB. If f==1 the USB will also stop if
		    an USB keyboard is assigned as stdin. The stdin
		    is then switched to serial input.
Storage USB Commands:
- usb scan:	    scans the USB for storage devices.The USB must be
		    running for this command (usb start)
- usb device [dev]: show or set current USB storage device
- usb part [dev]:   print partition table of one or all USB storage
		    devices
- usb read addr blk# cnt:
		    read `cnt' blocks starting at block `blk#'to
		    memory address `addr'
- usbboot addr dev:part:
		    boot from USB device

Config Switches:
----------------
CONFIG_CMD_USB	    enables basic USB support and the usb command
CONFIG_USB_UHCI	    defines the lowlevel part.A lowlevel part must be defined
		    if using CONFIG_CMD_USB
CONFIG_USB_KEYBOARD enables the USB Keyboard
CONFIG_USB_STORAGE  enables the USB storage devices
CONFIG_USB_HOST_ETHER	enables USB ethernet adapter support


USB Host Networking
===================

If you have a supported USB Ethernet adapter you can use it in U-Boot
to obtain an IP address and load a kernel from a network server.

Note: USB Host Networking is not the same as making your board act as a USB
client. In that case your board is pretending to be an Ethernet adapter
and will appear as a network interface to an attached computer. In that
case the connection is via a USB cable with the computer acting as the host.

With USB Host Networking, your board is the USB host. It controls the
Ethernet adapter to which it is directly connected and the connection to
the outside world is your adapter's Ethernet cable. Your board becomes an
independent network device, able to connect and perform network operations
independently of your computer.


Device support
--------------

Currently supported devices are listed in the drivers according to
their vendor and product IDs. You can check your device by connecting it
to a Linux machine and typing 'lsusb'. The drivers are in
drivers/usb/eth.

For example this lsusb output line shows a device with Vendor ID 0x0x95
and product ID 0x7720:

Bus 002 Device 010: ID 0b95:7720 ASIX Electronics Corp. AX88772

If you look at drivers/usb/eth/asix.c you will see this line within the
supported device list, so we know this adapter is supported.

	{ 0x0b95, 0x7720 },	/* Trendnet TU2-ET100 V3.0R */

If your adapter is not listed there is a still a chance that it will
work. Try looking up the manufacturer of the chip inside your adapter.
or take the adapter apart and look for chip markings. Then add a line
for your vendor/product ID into the table of the appropriate driver,
build U-Boot and see if it works. If not then there might be differences
between the chip in your adapter and the driver. You could try to get a
datasheet for your device and add support for it to U-Boot. This is not
particularly difficult - you only need to provide support for four basic
functions: init, halt, send and recv.


Enabling USB Host Networking
----------------------------

The normal U-Boot commands are used with USB networking, but you must
start USB first. For example:

usb start
setenv bootfile /tftpboot/uImage
bootp


To enable USB Host Ethernet in U-Boot, your platform must of course
support USB with CONFIG_CMD_USB enabled and working. You will need to
add some config settings to your board header file:

#define CONFIG_CMD_USB		/* the 'usb' interactive command */
#define CONFIG_USB_HOST_ETHER	/* Enable USB Ethernet adapters */

and one or more of the following for individual adapter hardware:

#define CONFIG_USB_ETHER_ASIX
#define CONFIG_USB_ETHER_MCS7830
#define CONFIG_USB_ETHER_SMSC95XX

As with built-in networking, you will also want to enable some network
commands, for example:

#define CONFIG_CMD_NET
#define CONFIG_CMD_PING
#define CONFIG_CMD_DHCP

and some bootp options, which tell your board to obtain its subnet,
gateway IP, host name and boot path from the bootp/dhcp server. These
settings should start you off:

#define CONFIG_BOOTP_SUBNETMASK
#define CONFIG_BOOTP_GATEWAY
#define CONFIG_BOOTP_HOSTNAME
#define CONFIG_BOOTP_BOOTPATH

You can also set the default IP address of your board and the server
as well as the default file to load when a 'bootp' command is issued.
However note that encoding these individual network settings into a
common exectuable is discouraged, as it leads to potential conflicts,
and all the parameters can either get stored in the board's external
environment, or get obtained from the bootp server if not set.

#define CONFIG_IPADDR		10.0.0.2  (replace with your value)
#define CONFIG_SERVERIP		10.0.0.1  (replace with your value)
#define CONFIG_BOOTFILE		"uImage"


The 'usb start' command should identify the adapter something like this:

CrOS> usb start
(Re)start USB...
USB EHCI 1.00
scanning bus for devices... 3 USB Device(s) found
       scanning bus for storage devices... 0 Storage Device(s) found
       scanning bus for ethernet devices... 1 Ethernet Device(s) found
CrOS> print ethact
ethact=asx0

You can see that it found an ethernet device and we can print out the
device name (asx0 in this case).

Then 'bootp' or 'dhcp' should use it to obtain an IP address from DHCP,
perhaps something like this:

CrOS> bootp
Waiting for Ethernet connection... done.
BOOTP broadcast 1
BOOTP broadcast 2
DHCP client bound to address 172.22.73.81
Using asx0 device
TFTP from server 172.22.72.144; our IP address is 172.22.73.81
Filename '/tftpboot/uImage-sjg-seaboard-261347'.
Load address: 0x40c000
Loading: #################################################################
	 #################################################################
	 #################################################################
	 ################################################
done
Bytes transferred = 3557464 (364858 hex)
CrOS>


Another way of doing this is to issue a tftp command, which will cause the
bootp to happen automatically.


MAC Addresses
-------------

Most Ethernet dongles have a built-in MAC address which is unique in the
world. This is important so that devices on the network can be
distinguised from each other. MAC address conflicts are evil and
generally result in strange and eratic behaviour.

Some boards have USB Ethernet chips on-board, and these sometimes do not
have an assigned MAC address. In this case it is up to you to assign
one which is unique. You should obtain a valid MAC address from a range
assigned to you before you ship the product.

Built-in Ethernet adapters support setting the MAC address by means of
an ethaddr environment variable for each interface (ethaddr, eth1addr,
eth2addr). There is similar support on the USB network side, using the
names usbethaddr, usbeth1addr, etc. They are kept separate since we
don't want a USB device taking the MAC address of a built-in device or
vice versa.

So if your USB Ethernet chip doesn't have a MAC address available then
you must set usbethaddr to a suitable MAC address. At the time of
writing this functionality is only supported by the SMSC driver.