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      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 2. Using imx_usb_loader for first install with SPL
     92 --------------------------------------------------
     93 
     94 imx_usb_loader is a very nice tool by Boundary Devices that
     95 allow to install U-Boot without a JTAG debugger, using
     96 the USB boot mode as described in the manual. It is
     97 a replacement for Freescale's MFGTOOLS.
     98 
     99 The sources can be found here:
    100 
    101 	https://github.com/boundarydevices/imx_usb_loader.git
    102 
    103 Booting in USB mode, the i.MX6 announces itself to the Linux Host as:
    104 
    105 Bus 001 Device 111: ID 15a2:0061 Freescale Semiconductor, Inc.
    106 
    107 imx_usb_loader is able to download a single file (u-boot.imx)
    108 to the board. For boards without SPL support, it is enough to
    109 issue the command:
    110 
    111 	sudo ../imx_usb_loader/imx_usb -v u-boot.imx
    112 
    113 In order to load SPL and u-boot.img via imx_usb_loader tool,
    114 please refer to doc/README.sdp.
    115 
    116