xref: /openbmc/u-boot/doc/imx/common/imx6.txt (revision 1a68faac)
1 U-Boot for Freescale i.MX6
2 
3 This file contains information for the port of U-Boot to the Freescale i.MX6
4 SoC.
5 
6 1. CONVENTIONS FOR FUSE ASSIGNMENTS
7 -----------------------------------
8 
9 1.1 MAC Address: It is stored in fuse bank 4, with the 32 lsbs in word 2 and the
10     16 msbs in word 3[15:0].
11     For i.MX6SX and i.MX6UL, they have two MAC addresses. The second MAC address
12     is stored in fuse bank 4, with the 16 lsb in word 3[31:16] and the 32 msbs in
13     word 4.
14 
15 Example:
16 
17 For reading the MAC address fuses on a MX6Q:
18 
19 - The MAC address is stored in two fuse addresses (the fuse addresses are
20 described in the Fusemap Descriptions table from the mx6q Reference Manual):
21 
22 0x620[31:0] - MAC_ADDR[31:0]
23 0x630[15:0] - MAC_ADDR[47:32]
24 
25 In order to use the fuse API, we need to pass the bank and word values, which
26 are calculated as below:
27 
28 Fuse address for the lower MAC address: 0x620
29 Base address for the fuses: 0x400
30 
31 (0x620 - 0x400)/0x10 = 0x22 = 34 decimal
32 
33 As the fuses are arranged in banks of 8 words:
34 
35 34 / 8 = 4 and the remainder is 2, so in this case:
36 
37 bank = 4
38 word = 2
39 
40 And the U-Boot command would be:
41 
42 => fuse read 4 2
43 Reading bank 4:
44 
45 Word 0x00000002: 9f027772
46 
47 Doing the same for the upper MAC address:
48 
49 Fuse address for the upper MAC address: 0x630
50 Base address for the fuses: 0x400
51 
52 (0x630 - 0x400)/0x10 = 0x23 = 35 decimal
53 
54 As the fuses are arranged in banks of 8 words:
55 
56 35 / 8 = 4 and the remainder is 3, so in this case:
57 
58 bank = 4
59 word = 3
60 
61 And the U-Boot command would be:
62 
63 => fuse read 4 3
64 Reading bank 4:
65 
66 Word 0x00000003: 00000004
67 
68 ,which matches the ethaddr value:
69 => echo ${ethaddr}
70 00:04:9f:02:77:72
71 
72 Some other useful hints:
73 
74 - The 'bank' and 'word' numbers can be easily obtained from the mx6 Reference
75 Manual. For the mx6quad case, please check the "46.5 OCOTP Memory Map/Register
76 Definition" from the "i.MX 6Dual/6Quad Applications Processor Reference Manual,
77 Rev. 1, 04/2013" document. For example, for the MAC fuses we have:
78 
79 Address:
80 21B_C620	Value of OTP Bank4 Word2 (MAC Address)(OCOTP_MAC0)
81 
82 21B_C630	Value of OTP Bank4 Word3 (MAC Address)(OCOTP_MAC1)
83 
84 - The command '=> fuse read 4 2 2' reads the whole MAC addresses at once:
85 
86 => fuse read 4 2 2
87 Reading bank 4:
88 
89 Word 0x00000002: 9f027772 00000004
90 
91