mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-18 10:48:51 +00:00
f1533c41a7
"valu" should be "value". Signed-off-by: Chris Packham <judge.packham@gmail.com> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
466 lines
16 KiB
ReStructuredText
466 lines
16 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
|
|
Environment Variables
|
|
=====================
|
|
|
|
U-Boot supports user configuration using environment variables which
|
|
can be made persistent by saving to persistent storage, for example flash
|
|
memory.
|
|
|
|
Environment variables are set using "env set" (alias "setenv"), printed using
|
|
"env print" (alias "printenv"), and saved to persistent storage using
|
|
"env save" (alias "saveenv"). Using "env set"
|
|
without a value can be used to delete a variable from the
|
|
environment. As long as you don't save the environment, you are
|
|
working with an in-memory copy. In case the Flash area containing the
|
|
environment is erased by accident, a default environment is provided.
|
|
|
|
See :doc:`cmd/env` for details.
|
|
|
|
Some configuration is controlled by Environment Variables, so that setting the
|
|
variable can adjust the behaviour of U-Boot (e.g. autoboot delay, autoloading
|
|
from tftp).
|
|
|
|
Text-based Environment
|
|
----------------------
|
|
|
|
The default environment for a board is created using a `.env` environment file
|
|
using a simple text format. The base filename for this is defined by
|
|
`CONFIG_ENV_SOURCE_FILE`, or `CONFIG_SYS_BOARD` if that is empty.
|
|
|
|
The file must be in the board directory and have a .env extension, so
|
|
assuming that there is a board vendor, the resulting filename is therefore::
|
|
|
|
board/<vendor>/<board>/<CONFIG_ENV_SOURCE_FILE>.env
|
|
|
|
or::
|
|
|
|
board/<vendor>/<board>/<CONFIG_SYS_BOARD>.env
|
|
|
|
This is a plain text file where you can type your environment variables in
|
|
the form `var=value`. Blank lines and multi-line variables are supported.
|
|
The conversion script looks for a line that starts in column 1 with a string
|
|
and has an equals sign immediately afterwards. Spaces before the = are not
|
|
permitted. It is a good idea to indent your scripts so that only the 'var='
|
|
appears at the start of a line.
|
|
|
|
To add additional text to a variable you can use `var+=value`. This text is
|
|
merged into the variable during the make process and made available as a
|
|
single value to U-Boot. Variables can contain `+` characters but in the unlikely
|
|
event that you want to have a variable name ending in plus, put a backslash
|
|
before the `+` so that the script knows you are not adding to an existing
|
|
variable but assigning to a new one::
|
|
|
|
maximum\+=value
|
|
|
|
This file can include C-style comments. Blank lines and multi-line
|
|
variables are supported, and you can use normal C preprocessor directives
|
|
and CONFIG defines from your board config also.
|
|
|
|
For example, for snapper9260 you would create a text file called
|
|
`board/bluewater/snapper9260.env` containing the environment text.
|
|
|
|
Example::
|
|
|
|
stdout=serial
|
|
#ifdef CONFIG_LCD
|
|
stdout+=,lcd
|
|
#endif
|
|
bootcmd=
|
|
/* U-Boot script for booting */
|
|
|
|
if [ -z ${tftpserverip} ]; then
|
|
echo "Use 'setenv tftpserverip a.b.c.d' to set IP address."
|
|
fi
|
|
|
|
usb start; setenv autoload n; bootp;
|
|
tftpboot ${tftpserverip}:
|
|
bootm
|
|
failed=
|
|
/* Print a message when boot fails */
|
|
echo CONFIG_SYS_BOARD boot failed - please check your image
|
|
echo Load address is CONFIG_SYS_LOAD_ADDR
|
|
|
|
If CONFIG_ENV_SOURCE_FILE is empty and the default filename is not present, then
|
|
the old-style C environment is used instead. See below.
|
|
|
|
Old-style C environment
|
|
-----------------------
|
|
|
|
Traditionally, the default environment is created in `include/env_default.h`,
|
|
and can be augmented by various `CONFIG` defines. See that file for details. In
|
|
particular you can define `CONFIG_EXTRA_ENV_SETTINGS` in your board file
|
|
to add environment variables.
|
|
|
|
Board maintainers are encouraged to migrate to the text-based environment as it
|
|
is easier to maintain. The distro-board script still requires the old-style
|
|
environment but work is underway to address this.
|
|
|
|
|
|
List of environment variables
|
|
-----------------------------
|
|
|
|
Some device configuration options can be set using environment variables. In
|
|
many cases the value in the default environment comes from a CONFIG option - see
|
|
`include/env_default.h`) for this.
|
|
|
|
This is most-likely not complete:
|
|
|
|
baudrate
|
|
Used to set the baudrate of the UART - it defaults to CONFIG_BAUDRATE (which
|
|
defaults to 115200).
|
|
|
|
bootdelay
|
|
Delay before automatically running bootcmd. During this time the user
|
|
can choose to enter the shell (or the boot menu if
|
|
CONFIG_AUTOBOOT_MENU_SHOW=y):
|
|
|
|
- 0 to autoboot with no delay, but you can stop it by key input.
|
|
- -1 to disable autoboot.
|
|
- -2 to autoboot with no delay and not check for abort
|
|
|
|
The default value is defined by CONFIG_BOOTDELAY.
|
|
The value of 'bootdelay' is overridden by the /config/bootdelay value in
|
|
the device-tree if CONFIG_OF_CONTROL=y.
|
|
|
|
bootcmd
|
|
The command that is run if the user does not enter the shell during the
|
|
boot delay.
|
|
|
|
bootargs
|
|
Command line arguments passed when booting an operating system or binary
|
|
image
|
|
|
|
bootfile
|
|
Name of the image to load with TFTP
|
|
|
|
bootm_low
|
|
Memory range available for image processing in the bootm
|
|
command can be restricted. This variable is given as
|
|
a hexadecimal number and defines lowest address allowed
|
|
for use by the bootm command. See also "bootm_size"
|
|
environment variable. Address defined by "bootm_low" is
|
|
also the base of the initial memory mapping for the Linux
|
|
kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
|
|
bootm_mapsize.
|
|
|
|
bootm_mapsize
|
|
Size of the initial memory mapping for the Linux kernel.
|
|
This variable is given as a hexadecimal number and it
|
|
defines the size of the memory region starting at base
|
|
address bootm_low that is accessible by the Linux kernel
|
|
during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
|
|
as the default value if it is defined, and bootm_size is
|
|
used otherwise.
|
|
|
|
bootm_size
|
|
Memory range available for image processing in the bootm
|
|
command can be restricted. This variable is given as
|
|
a hexadecimal number and defines the size of the region
|
|
allowed for use by the bootm command. See also "bootm_low"
|
|
environment variable.
|
|
|
|
bootstopkeysha256, bootdelaykey, bootstopkey
|
|
See README.autoboot
|
|
|
|
updatefile
|
|
Location of the software update file on a TFTP server, used
|
|
by the automatic software update feature. Please refer to
|
|
documentation in doc/README.update for more details.
|
|
|
|
autoload
|
|
if set to "no" (any string beginning with 'n'),
|
|
"bootp" and "dhcp" will just load perform a lookup of the
|
|
configuration from the BOOTP server, but not try to
|
|
load any image.
|
|
|
|
autostart
|
|
if set to "yes", an image loaded using the "bootp", "dhcp",
|
|
"rarpboot", "tftpboot" or "diskboot" commands will
|
|
be automatically started (by internally calling
|
|
"bootm")
|
|
|
|
If unset, or set to "1"/"yes"/"true" (case insensitive, just the first
|
|
character is enough), a standalone image
|
|
passed to the "bootm" command will be copied to the load address
|
|
(and eventually uncompressed), but NOT be started.
|
|
This can be used to load and uncompress arbitrary
|
|
data.
|
|
|
|
fdt_high
|
|
if set this restricts the maximum address that the
|
|
flattened device tree will be copied into upon boot.
|
|
For example, if you have a system with 1 GB memory
|
|
at physical address 0x10000000, while Linux kernel
|
|
only recognizes the first 704 MB as low memory, you
|
|
may need to set fdt_high as 0x3C000000 to have the
|
|
device tree blob be copied to the maximum address
|
|
of the 704 MB low memory, so that Linux kernel can
|
|
access it during the boot procedure.
|
|
|
|
If this is set to the special value 0xffffffff (32-bit machines) or
|
|
0xffffffffffffffff (64-bit machines) then
|
|
the fdt will not be copied at all on boot. For this
|
|
to work it must reside in writable memory, have
|
|
sufficient padding on the end of it for u-boot to
|
|
add the information it needs into it, and the memory
|
|
must be accessible by the kernel.
|
|
|
|
fdtcontroladdr
|
|
if set this is the address of the control flattened
|
|
device tree used by U-Boot when CONFIG_OF_CONTROL is
|
|
defined.
|
|
|
|
initrd_high
|
|
restrict positioning of initrd images:
|
|
If this variable is not set, initrd images will be
|
|
copied to the highest possible address in RAM; this
|
|
is usually what you want since it allows for
|
|
maximum initrd size. If for some reason you want to
|
|
make sure that the initrd image is loaded below the
|
|
CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
|
|
variable to a value of "no" or "off" or "0".
|
|
Alternatively, you can set it to a maximum upper
|
|
address to use (U-Boot will still check that it
|
|
does not overwrite the U-Boot stack and data).
|
|
|
|
For instance, when you have a system with 16 MB
|
|
RAM, and want to reserve 4 MB from use by Linux,
|
|
you can do this by adding "mem=12M" to the value of
|
|
the "bootargs" variable. However, now you must make
|
|
sure that the initrd image is placed in the first
|
|
12 MB as well - this can be done with::
|
|
|
|
setenv initrd_high 00c00000
|
|
|
|
If you set initrd_high to 0xffffffff (32-bit machines) or
|
|
0xffffffffffffffff (64-bit machines), this is an
|
|
indication to U-Boot that all addresses are legal
|
|
for the Linux kernel, including addresses in flash
|
|
memory. In this case U-Boot will NOT COPY the
|
|
ramdisk at all. This may be useful to reduce the
|
|
boot time on your system, but requires that this
|
|
feature is supported by your Linux kernel.
|
|
|
|
ipaddr
|
|
IP address; needed for tftpboot command
|
|
|
|
loadaddr
|
|
Default load address for commands like "bootp",
|
|
"rarpboot", "tftpboot", "loadb" or "diskboot"
|
|
|
|
loads_echo
|
|
see CONFIG_LOADS_ECHO
|
|
|
|
serverip
|
|
TFTP server IP address; needed for tftpboot command
|
|
|
|
bootretry
|
|
see CONFIG_BOOT_RETRY_TIME
|
|
|
|
bootdelaykey
|
|
see CONFIG_AUTOBOOT_DELAY_STR
|
|
|
|
bootstopkey
|
|
see CONFIG_AUTOBOOT_STOP_STR
|
|
|
|
ethprime
|
|
controls which network interface is used first.
|
|
|
|
ethact
|
|
controls which interface is currently active.
|
|
For example you can do the following::
|
|
|
|
=> setenv ethact FEC
|
|
=> ping 192.168.0.1 # traffic sent on FEC
|
|
=> setenv ethact SCC
|
|
=> ping 10.0.0.1 # traffic sent on SCC
|
|
|
|
ethrotate
|
|
When set to "no" U-Boot does not go through all
|
|
available network interfaces.
|
|
It just stays at the currently selected interface. When unset or set to
|
|
anything other than "no", U-Boot does go through all
|
|
available network interfaces.
|
|
|
|
netretry
|
|
When set to "no" each network operation will
|
|
either succeed or fail without retrying.
|
|
When set to "once" the network operation will
|
|
fail when all the available network interfaces
|
|
are tried once without success.
|
|
Useful on scripts which control the retry operation
|
|
themselves.
|
|
|
|
silent_linux
|
|
If set then Linux will be told to boot silently, by
|
|
adding 'console=' to its command line. If "yes" it will be
|
|
made silent. If "no" it will not be made silent. If
|
|
unset, then it will be made silent if the U-Boot console
|
|
is silent.
|
|
|
|
tftpsrcp
|
|
If this is set, the value is used for TFTP's
|
|
UDP source port.
|
|
|
|
tftpdstp
|
|
If this is set, the value is used for TFTP's UDP
|
|
destination port instead of the default port 69.
|
|
|
|
tftpblocksize
|
|
Block size to use for TFTP transfers; if not set,
|
|
we use the TFTP server's default block size
|
|
|
|
tftptimeout
|
|
Retransmission timeout for TFTP packets (in milli-
|
|
seconds, minimum value is 1000 = 1 second). Defines
|
|
when a packet is considered to be lost so it has to
|
|
be retransmitted. The default is 5000 = 5 seconds.
|
|
Lowering this value may make downloads succeed
|
|
faster in networks with high packet loss rates or
|
|
with unreliable TFTP servers.
|
|
|
|
tftptimeoutcountmax
|
|
maximum count of TFTP timeouts (no
|
|
unit, minimum value = 0). Defines how many timeouts
|
|
can happen during a single file transfer before that
|
|
transfer is aborted. The default is 10, and 0 means
|
|
'no timeouts allowed'. Increasing this value may help
|
|
downloads succeed with high packet loss rates, or with
|
|
unreliable TFTP servers or client hardware.
|
|
|
|
tftpwindowsize
|
|
if this is set, the value is used for TFTP's
|
|
window size as described by RFC 7440.
|
|
This means the count of blocks we can receive before
|
|
sending ack to server.
|
|
|
|
vlan
|
|
When set to a value < 4095 the traffic over
|
|
Ethernet is encapsulated/received over 802.1q
|
|
VLAN tagged frames.
|
|
|
|
Note: This appears not to be used in U-Boot. See `README.VLAN`.
|
|
|
|
bootpretryperiod
|
|
Period during which BOOTP/DHCP sends retries.
|
|
Unsigned value, in milliseconds. If not set, the period will
|
|
be either the default (28000), or a value based on
|
|
CONFIG_NET_RETRY_COUNT, if defined. This value has
|
|
precedence over the value based on CONFIG_NET_RETRY_COUNT.
|
|
|
|
memmatches
|
|
Number of matches found by the last 'ms' command, in hex
|
|
|
|
memaddr
|
|
Address of the last match found by the 'ms' command, in hex,
|
|
or 0 if none
|
|
|
|
mempos
|
|
Index position of the last match found by the 'ms' command,
|
|
in units of the size (.b, .w, .l) of the search
|
|
|
|
zbootbase
|
|
(x86 only) Base address of the bzImage 'setup' block
|
|
|
|
zbootaddr
|
|
(x86 only) Address of the loaded bzImage, typically
|
|
BZIMAGE_LOAD_ADDR which is 0x100000
|
|
|
|
|
|
Image locations
|
|
---------------
|
|
|
|
The following image location variables contain the location of images
|
|
used in booting. The "Image" column gives the role of the image and is
|
|
not an environment variable name. The other columns are environment
|
|
variable names. "File Name" gives the name of the file on a TFTP
|
|
server, "RAM Address" gives the location in RAM the image will be
|
|
loaded to, and "Flash Location" gives the image's address in NOR
|
|
flash or offset in NAND flash.
|
|
|
|
*Note* - these variables don't have to be defined for all boards, some
|
|
boards currently use other variables for these purposes, and some
|
|
boards use these variables for other purposes.
|
|
|
|
Also note that most of these variables are just a commonly used set of variable
|
|
names, used in some other variable definitions, but are not hard-coded anywhere
|
|
in U-Boot code.
|
|
|
|
================= ============== ================ ==============
|
|
Image File Name RAM Address Flash Location
|
|
================= ============== ================ ==============
|
|
u-boot u-boot u-boot_addr_r u-boot_addr
|
|
Linux kernel bootfile kernel_addr_r kernel_addr
|
|
device tree blob fdtfile fdt_addr_r fdt_addr
|
|
ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
|
|
================= ============== ================ ==============
|
|
|
|
|
|
Automatically updated variables
|
|
-------------------------------
|
|
|
|
The following environment variables may be used and automatically
|
|
updated by the network boot commands ("bootp" and "rarpboot"),
|
|
depending the information provided by your boot server:
|
|
|
|
========= ===================================================
|
|
Variable Notes
|
|
========= ===================================================
|
|
bootfile see above
|
|
dnsip IP address of your Domain Name Server
|
|
dnsip2 IP address of your secondary Domain Name Server
|
|
gatewayip IP address of the Gateway (Router) to use
|
|
hostname Target hostname
|
|
ipaddr See above
|
|
netmask Subnet Mask
|
|
rootpath Pathname of the root filesystem on the NFS server
|
|
serverip see above
|
|
========= ===================================================
|
|
|
|
|
|
Special environment variables
|
|
-----------------------------
|
|
|
|
There are two special Environment Variables:
|
|
|
|
serial#
|
|
contains hardware identification information such as type string and/or
|
|
serial number
|
|
ethaddr
|
|
Ethernet address. If CONFIG_REGEX=y, also eth*addr (where * is an integer).
|
|
|
|
These variables can be set only once (usually during manufacturing of
|
|
the board). U-Boot refuses to delete or overwrite these variables
|
|
once they have been set, unless CONFIG_ENV_OVERWRITE is enabled in the board
|
|
configuration.
|
|
|
|
Also:
|
|
|
|
ver
|
|
Contains the U-Boot version string as printed
|
|
with the "version" command. This variable is
|
|
readonly (see CONFIG_VERSION_VARIABLE).
|
|
|
|
Please note that changes to some configuration parameters may take
|
|
only effect after the next boot (yes, that's just like Windows).
|
|
|
|
|
|
External environment file
|
|
-------------------------
|
|
|
|
The `CONFIG_USE_DEFAULT_ENV_FILE` option provides a way to bypass the
|
|
environment generation in U-Boot. If enabled, then `CONFIG_DEFAULT_ENV_FILE`
|
|
provides the name of a file which is converted into the environment,
|
|
completely bypassing the standard environment variables in `env_default.h`.
|
|
|
|
The format is the same as accepted by the mkenvimage tool, with lines containing
|
|
key=value pairs. Blank lines and lines beginning with # are ignored.
|
|
|
|
Future work may unify this feature with the text-based environment, perhaps
|
|
moving the contents of `env_default.h` to a text file.
|
|
|
|
Implementation
|
|
--------------
|
|
|
|
See :doc:`../develop/environment` for internal development details.
|