1/* 2 * (C) Copyright 2001 3 * Dave Ellis, SIXNET, dge@sixnetio.com 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 24Using autoboot configuration options 25==================================== 26 27The basic autoboot configuration options are documented in the main 28U-Boot README. See it for details. They are: 29 30 bootdelay 31 bootcmd 32 CONFIG_BOOTDELAY 33 CONFIG_BOOTCOMMAND 34 35Some additional options that make autoboot safer in a production 36product are documented here. 37 38Why use them? 39------------- 40 41The basic autoboot feature allows a system to automatically boot to 42the real application (such as Linux) without a user having to enter 43any commands. If any key is pressed before the boot delay time 44expires, U-Boot stops the autoboot process, gives a U-Boot prompt 45and waits forever for a command. That's a good thing if you pressed a 46key because you wanted to get the prompt. 47 48It's not so good if the key press was a stray character on the 49console serial port, say because a user who knows nothing about 50U-Boot pressed a key before the system had time to boot. It's even 51worse on an embedded product that doesn't have a console during 52normal use. The modem plugged into that console port sends a 53character at the wrong time and the system hangs, with no clue as to 54why it isn't working. 55 56You might want the system to autoboot to recover after an external 57configuration program stops autoboot. If the configuration program 58dies or loses its connection (modems can disconnect at the worst 59time) U-Boot will patiently wait forever for it to finish. 60 61These additional configuration options can help provide a system that 62boots when it should, but still allows access to U-Boot. 63 64What they do 65------------ 66 67 CONFIG_BOOT_RETRY_TIME 68 CONFIG_BOOT_RETRY_MIN 69 70 bootretry environment variable 71 72 These options determine what happens after autoboot is 73 stopped and U-Boot is waiting for commands. 74 75 CONFIG_BOOT_RETRY_TIME must be defined to enable the boot 76 retry feature. If the environment variable 'bootretry' is 77 found then its value is used, otherwise the retry timeout is 78 CONFIG_BOOT_RETRY_TIME. CONFIG_BOOT_RETRY_MIN is optional and 79 defaults to CONFIG_BOOT_RETRY_TIME. All times are in seconds. 80 81 If the retry timeout is negative, the U-Boot command prompt 82 never times out. Otherwise it is forced to be at least 83 CONFIG_BOOT_RETRY_MIN seconds. If no valid U-Boot command is 84 entered before the specified time the boot delay sequence is 85 restarted. Each command that U-Boot executes restarts the 86 timeout. 87 88 If CONFIG_BOOT_RETRY_TIME < 0 the feature is there, but 89 doesn't do anything unless the environment variable 90 'bootretry' is >= 0. 91 92 CONFIG_AUTOBOOT_KEYED 93 CONFIG_AUTOBOOT_PROMPT 94 CONFIG_AUTOBOOT_DELAY_STR 95 CONFIG_AUTOBOOT_STOP_STR 96 CONFIG_AUTOBOOT_DELAY_STR2 97 CONFIG_AUTOBOOT_STOP_STR2 98 99 bootdelaykey environment variable 100 bootstopkey environment variable 101 bootdelaykey2 environment variable 102 bootstopkey2 environment variable 103 104 These options give more control over stopping autoboot. When 105 they are used a specific character or string is required to 106 stop or delay autoboot. 107 108 Define CONFIG_AUTOBOOT_KEYED (no value required) to enable 109 this group of options. CONFIG_AUTOBOOT_DELAY_STR, 110 CONFIG_AUTOBOOT_STOP_STR or both should be specified (or 111 specified by the corresponding environment variable), 112 otherwise there is no way to stop autoboot. 113 114 CONFIG_AUTOBOOT_PROMPT is displayed before the boot delay 115 selected by CONFIG_BOOTDELAY starts. If it is not defined 116 there is no output indicating that autoboot is in progress. 117 If "%d" is included, it is replaced by the number of seconds 118 remaining before autoboot will start, but it does not count 119 down the seconds. "autoboot in %d seconds\n" is a reasonable 120 prompt. 121 122 If CONFIG_AUTOBOOT_DELAY_STR or bootdelaykey is specified and 123 this string is received from console input before autoboot 124 starts booting, U-Boot gives a command prompt. The U-Boot 125 prompt will time out if CONFIG_BOOT_RETRY_TIME is used, 126 otherwise it never times out. 127 128 If CONFIG_AUTOBOOT_STOP_STR or bootstopkey is specified and 129 this string is received from console input before autoboot 130 starts booting, U-Boot gives a command prompt. The U-Boot 131 prompt never times out, even if CONFIG_BOOT_RETRY_TIME is 132 used. 133 134 The string recognition is not very sophisticated. If a 135 partial match is detected, the first non-matching character 136 is checked to see if starts a new match. There is no check 137 for a shorter partial match, so it's best if the first 138 character of a key string does not appear in the rest of the 139 string. 140 141 Using the CONFIG_AUTOBOOT_DELAY_STR2 / bootdelaykey2 and/or 142 CONFIG_AUTOBOOT_STOP_STR2 / bootstopkey #defines and/or 143 environment variables you can specify a second, alternate 144 string (which allows you to haw two "password" strings). 145 146 CONFIG_ZERO_BOOTDELAY_CHECK 147 148 If this option is defined, you can stop the autoboot process 149 by hitting a key even in that case when "bootdelay" has been 150 set to 0. You can set "bootdelay" to a negative value to 151 prevent the check for console input. 152 153 CONFIG_RESET_TO_RETRY 154 155 (Only effective when CONFIG_BOOT_RETRY_TIME is also set) 156 After the countdown timed out, the board will be reset to restart 157 again. 158 159