1Device Firmware Upgrade (DFU) - extension to use TFTP 2===================================================== 3 4Why? 5---- 6 7* Update TFTP (CONFIG_UPDATE_TFTP) only supports writing 8code to NAND memory via TFTP. 9* DFU supports writing data to the variety of mediums (NAND, 10eMMC, SD, partitions, RAM, etc) via USB. 11 12Combination of both solves their shortcomings! 13 14 15Overview 16-------- 17 18This document briefly describes how to use DFU for 19upgrading firmware (e.g. kernel, u-boot, rootfs, etc.) 20via TFTP protocol. 21 22By using Ethernet (TFTP protocol to be precise) it is 23possible to overcome the major problem of USB based DFU - 24the relatively low transfer speed for large files. 25This was caused by DFU standard, which imposed utilization 26of only EP0 for transfer. By using Ethernet we can circumvent 27this shortcoming. 28 29Beagle Bone Black rev. C (BBB) powered by TI's am335x CPU has 30been used as a demo board. 31 32To utilize this feature, one needs to first enable support 33for USB based DFU (CONFIG_DFU_*) and DFU TFTP update 34(CONFIG_DFU_TFTP) described in ./doc/README.update. 35 36The "dfu" command has been extended to support transfer via TFTP - one 37needs to type for example "dfu tftp 0 mmc 0" 38 39This feature does not depend on "fitupd" command enabled. 40 41As of this writing (SHA1:8d77576371381ade83de475bb639949b44941e8c v2015.10-rc2) 42the update.c code is not enabled (CONFIG_UPDATE_TFTP) by any board in the 43contemporary u-boot tree. 44 45 46Environment variables 47--------------------- 48 49The "dfu tftp" command can be used in the "preboot" environment variable 50(when it is enabled by defining CONFIG_PREBOOT). 51This is the preferable way of using this command in the early boot stage 52as opposed to legacy update_tftp() function invocation. 53 54 55Beagle Bone Black (BBB) setup 56----------------------------- 57 581. Setup tftp env variables: 59 * select desired eth device - 'ethact' variable ["ethact=cpsw"] 60 (use "bdinfo" to check current setting) 61 * setup "serverip" and "ipaddr" variables 62 * set "loadaddr" as a fixed buffer where incoming data is placed 63 ["loadaddr=0x81000000"] 64 65######### 66# BONUS # 67######### 68It is possible to use USB interface to emulate ETH connection by setting 69"ethact=usb_ether". In this way one can have very fast DFU transfer via USB. 70 71For 33MiB test image the transfer rate was 1MiB/s for ETH over USB and 200KiB/s 72for pure DFU USB transfer. 73 742. Setup update_tftp variables: 75 * set "updatefile" - the file name to be downloaded via TFTP (stored on 76 the HOST at e.g. /srv/tftp) 77 783. If required, to update firmware on boot, put the "dfu tftp 0 mmc 0" in the 79 "preboot" env variable. Otherwise use this command from u-boot prompt. 80 814. Inspect "dfu" specific variables: 82 * "dfu_alt_info" - information about available DFU entities 83 * "dfu_bufsiz" - variable to set buffer size [in bytes] - when it is not 84 possible to set large enough default buffer (8 MiB @ BBB) 85 86 87 88FIT image format for download 89----------------------------- 90 91To create FIT image for download one should follow the update tftp README file 92(./doc/README.update) with one notable difference: 93 94The original snippet of ./doc/uImage.FIT/update_uboot.its 95 96 images { 97 update@1 { 98 description = "U-Boot binary"; 99 100should look like 101 102 images { 103 u-boot.bin@1 { 104 description = "U-Boot binary"; 105 106where "u-boot.bin" is the DFU entity name to be stored. 107 108 109 110To do 111----- 112 113* Extend dfu-util command to support TFTP based transfers 114* Upload support (via TFTP) 115