U-Boot for Freescale i.MX6
  
  This file contains information for the port of U-Boot to the Freescale i.MX6
  SoC.
  
  1. CONVENTIONS FOR FUSE ASSIGNMENTS
  -----------------------------------
  
  1.1 MAC Address: It is stored in fuse bank 4, with the 32 lsbs in word 2 and the

      16 msbs in word 3[15:0].
      For i.MX6SX and i.MX6UL, they have two MAC addresses. The second MAC address
      is stored in fuse bank 4, with the 16 lsb in word 3[31:16] and the 32 msbs in 
      word 4.

  
  Example:
  
  For reading the MAC address fuses on a MX6Q:
  
  - The MAC address is stored in two fuse addresses (the fuse addresses are
  described in the Fusemap Descriptions table from the mx6q Reference Manual):
  
  0x620[31:0] - MAC_ADDR[31:0]
  0x630[15:0] - MAC_ADDR[47:32]
  
  In order to use the fuse API, we need to pass the bank and word values, which
  are calculated as below:
  
  Fuse address for the lower MAC address: 0x620
  Base address for the fuses: 0x400
  
  (0x620 - 0x400)/0x10 = 0x22 = 34 decimal
  
  As the fuses are arranged in banks of 8 words:
  
  34 / 8 = 4 and the remainder is 2, so in this case:
  
  bank = 4
  word = 2

  And the U-Boot command would be:

  
  => fuse read 4 2
  Reading bank 4:
  
  Word 0x00000002: 9f027772
  
  Doing the same for the upper MAC address:
  
  Fuse address for the upper MAC address: 0x630
  Base address for the fuses: 0x400
  
  (0x630 - 0x400)/0x10 = 0x23 = 35 decimal
  
  As the fuses are arranged in banks of 8 words:
  
  35 / 8 = 4 and the remainder is 3, so in this case:
  
  bank = 4
  word = 3

  And the U-Boot command would be:

  
  => fuse read 4 3
  Reading bank 4:
  
  Word 0x00000003: 00000004
  
  ,which matches the ethaddr value:
  => echo ${ethaddr}
  00:04:9f:02:77:72
  
  Some other useful hints:
  
  - The 'bank' and 'word' numbers can be easily obtained from the mx6 Reference
  Manual. For the mx6quad case, please check the "46.5 OCOTP Memory Map/Register
  Definition" from the "i.MX 6Dual/6Quad Applications Processor Reference Manual,
  Rev. 1, 04/2013" document. For example, for the MAC fuses we have:
  
  Address:
  21B_C620	Value of OTP Bank4 Word2 (MAC Address)(OCOTP_MAC0)
  
  21B_C630	Value of OTP Bank4 Word3 (MAC Address)(OCOTP_MAC1)
  
  - The command '=> fuse read 4 2 2' reads the whole MAC addresses at once:
  
  => fuse read 4 2 2
  Reading bank 4:
  
  Word 0x00000002: 9f027772 00000004

  
  2. Using imx_usb_loader for first install with SPL
  --------------------------------------------------
  
  imx_usb_loader is a very nice tool by BoundaryDevice that
  allow to install U-Boot without a JTAG debugger, using
  the USB boot mode as described in the manual. It is
  a replacement for Freescale's MFGTOOLS.
  
  The sources can be found here:
  
  	https://github.com/boundarydevices/imx_usb_loader.git
  
  Booting in USB mode, the i.MX6 announces itself to the Linux Host as:
  
  Bus 001 Device 111: ID 15a2:0061 Freescale Semiconductor, Inc.
  
  imx_usb_loader is able to download a single file (u-boot.imx)
  to the board. For boards without SPL support, it is enough to
  issue the command:
  
  	sudo ../imx_usb_loader/imx_usb -v u-boot.imx
  
  Getting U-Boot when SPL support is active, it requires
  two downloads. imx_usb_loader downloads the SPL into
  OCRAM and starts it. SPL will check for a valid u-boot.img, and
  because it is not found, it will wait for it using the y-modem
  protocol via the console.
  
  A first install is then possible by combining imx_usb_loader with
  another tool such as kermit.
  
  sudo ../imx_usb_loader/imx_usb -v SPL
  kermit kermit_uboot
  
  and kermit_uboot contains something like this (set line should be adjusted):
  
  set line /dev/ttyUSB1
  set speed 115200
  SET CARRIER-WATCH OFF
  set flow-control none
  set handshake none
  set prefixing all
  set file type bin
  set protocol ymodem
  send u-boot.img
  c
  
  The last "c" command tells kermit (from ckermit package in most distros)
  to switch from command line mode to communication mode, and when the
  script is finished, the U-Boot prompt is shown in the same shell.