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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)