1# SPDX-License-Identifier: GPL-2.0+ 2# 3# Copyright (C) 2015 4# 5# Lukasz Majewski <l.majewski@majess.pl> 6 7Device Firmware Upgrade (DFU) - extension to use TFTP 8===================================================== 9 10Why? 11---- 12 13* Update TFTP (CONFIG_UPDATE_TFTP) only supports writing 14code to NAND memory via TFTP. 15* DFU supports writing data to the variety of mediums (NAND, 16eMMC, SD, partitions, RAM, etc) via USB. 17 18Combination of both solves their shortcomings! 19 20 21Overview 22-------- 23 24This document briefly describes how to use DFU for 25upgrading firmware (e.g. kernel, u-boot, rootfs, etc.) 26via TFTP protocol. 27 28By using Ethernet (TFTP protocol to be precise) it is 29possible to overcome the major problem of USB based DFU - 30the relatively low transfer speed for large files. 31This was caused by DFU standard, which imposed utilization 32of only EP0 for transfer. By using Ethernet we can circumvent 33this shortcoming. 34 35Beagle Bone Black rev. C (BBB) powered by TI's am335x CPU has 36been used as a demo board. 37 38To utilize this feature, one needs to first enable support 39for USB based DFU (CONFIG_DFU_*) and DFU TFTP update 40(CONFIG_DFU_TFTP) described in ./doc/README.update. 41 42The "dfu" command has been extended to support transfer via TFTP - one 43needs to type for example "dfu tftp 0 mmc 0" 44 45As of this writing (SHA1:8d77576371381ade83de475bb639949b44941e8c v2015.10-rc2) 46the update.c code is not enabled (CONFIG_UPDATE_TFTP) by any board in the 47contemporary u-boot tree. 48 49 50Environment variables 51--------------------- 52 53The "dfu tftp" command can be used in the "preboot" environment variable 54(when it is enabled by defining CONFIG_PREBOOT). 55This is the preferable way of using this command in the early boot stage 56as opposed to legacy update_tftp() function invocation. 57 58 59Beagle Bone Black (BBB) setup 60----------------------------- 61 621. Setup tftp env variables: 63 * select desired eth device - 'ethact' variable ["ethact=cpsw"] 64 (use "bdinfo" to check current setting) 65 * setup "serverip" and "ipaddr" variables 66 * set "loadaddr" as a fixed buffer where incoming data is placed 67 ["loadaddr=0x81000000"] 68 69######### 70# BONUS # 71######### 72It is possible to use USB interface to emulate ETH connection by setting 73"ethact=usb_ether". In this way one can have very fast DFU transfer via USB. 74 75For 33MiB test image the transfer rate was 1MiB/s for ETH over USB and 200KiB/s 76for pure DFU USB transfer. 77 782. Setup update_tftp variables: 79 * set "updatefile" - the file name to be downloaded via TFTP (stored on 80 the HOST at e.g. /srv/tftp) 81 823. If required, to update firmware on boot, put the "dfu tftp 0 mmc 0" in the 83 "preboot" env variable. Otherwise use this command from u-boot prompt. 84 854. Inspect "dfu" specific variables: 86 * "dfu_alt_info" - information about available DFU entities 87 * "dfu_bufsiz" - variable to set buffer size [in bytes] - when it is not 88 possible to set large enough default buffer (8 MiB @ BBB) 89 90 91 92FIT image format for download 93----------------------------- 94 95To create FIT image for download one should follow the update tftp README file 96(./doc/README.update) with one notable difference: 97 98The original snippet of ./doc/uImage.FIT/update_uboot.its 99 100 images { 101 update@1 { 102 description = "U-Boot binary"; 103 104should look like 105 106 images { 107 u-boot.bin@1 { 108 description = "U-Boot binary"; 109 110where "u-boot.bin" is the DFU entity name to be stored. 111 112 113 114To do 115----- 116 117* Extend dfu-util command to support TFTP based transfers 118* Upload support (via TFTP) 119