1Automatic software update from a TFTP server 2============================================ 3 4Overview 5-------- 6 7This feature allows to automatically store software updates present on a TFTP 8server in NOR Flash. In more detail: a TFTP transfer of a file given in 9environment variable 'updatefile' from server 'serverip' is attempted during 10boot. The update file should be a FIT file, and can contain one or more 11updates. Each update in the update file has an address in NOR Flash where it 12should be placed, updates are also protected with a SHA-1 checksum. If the 13TFTP transfer is successful, the hash of each update is verified, and if the 14verification is positive, the update is stored in Flash. 15 16The auto-update feature is enabled by the CONFIG_UPDATE_TFTP macro: 17 18#define CONFIG_UPDATE_TFTP 1 19 20 21Note that when enabling auto-update, Flash support must be turned on. Also, 22one must enable FIT and LIBFDT support: 23 24#define CONFIG_FIT 1 25#define CONFIG_OF_LIBFDT 1 26 27The auto-update feature uses the following configuration knobs: 28 29- CONFIG_UPDATE_LOAD_ADDR 30 31 Normally, TFTP transfer of the update file is done to the address specified 32 in environment variable 'loadaddr'. If this variable is not present, the 33 transfer is made to the address given in CONFIG_UPDATE_LOAD_ADDR (0x100000 34 by default). 35 36- CONFIG_UPDATE_TFTP_CNT_MAX 37 CONFIG_UPDATE_TFTP_MSEC_MAX 38 39 These knobs control the timeouts during initial connection to the TFTP 40 server. Since a transfer is attempted during each boot, it is undesirable to 41 have a long delay when a TFTP server is not present. 42 CONFIG_UPDATE_TFTP_MSEC_MAX specifies the number of milliseconds to wait for 43 the server to respond to initial connection, and CONFIG_UPDATE_TFTP_CNT_MAX 44 gives the number of such connection retries. CONFIG_UPDATE_TFTP_CNT_MAX must 45 be non-negative and is 0 by default, CONFIG_UPDATE_TFTP_MSEC_MAX must be 46 positive and is 100 by default. 47 48Since the update file is in FIT format, it is created from an *.its file using 49the mkimage tool. dtc tool with support for binary includes, e.g. in version 501.2.0 or later, must also be available on the system where the update file is 51to be prepared. Refer to the doc/uImage.FIT/ directory for more details on FIT 52images. 53 54This mechanism can be also triggered by the commmand "fitupd". 55If an optional, non-zero address is provided as argument, the TFTP transfer 56is skipped and the image at this address is used. 57The fitupd command is enabled by CONFIG_CMD_FITUPD. 58 59 60Example .its files 61------------------ 62 63- doc/uImage.FIT/update_uboot.its 64 65 A simple example that can be used to create an update file for automatically 66 replacing U-Boot image on a system. 67 68 Assuming that an U-Boot image u-boot.bin is present in the current working 69 directory, and that the address given in the 'load' property in the 70 'update_uboot.its' file is where the U-Boot is stored in Flash, the 71 following command will create the actual update file 'update_uboot.itb': 72 73 mkimage -f update_uboot.its update_uboot.itb 74 75 Place 'update_uboot.itb' on a TFTP server, for example as 76 '/tftpboot/update_uboot.itb', and set the 'updatefile' variable 77 appropriately, for example in the U-Boot prompt: 78 79 setenv updatefile /tftpboot/update_uboot.itb 80 saveenv 81 82 Now, when the system boots up and the update TFTP server specified in the 83 'serverip' environment variable is accessible, the new U-Boot image will be 84 automatically stored in Flash. 85 86 NOTE: do make sure that the 'u-boot.bin' image used to create the update 87 file is a good, working image. Also make sure that the address in Flash 88 where the update will be placed is correct. Making mistake here and 89 attempting the auto-update can render the system unusable. 90 91- doc/uImage.FIT/update3.its 92 93 An example containing three updates. It can be used to update Linux kernel, 94 ramdisk and FDT blob stored in Flash. The procedure for preparing the update 95 file is similar to the example above. 96