Setting up U-Boot

U-Boot

U-Boot is another popular boot loader. A preliminary port to the Xtensa architecture is now available. See U-Boot Sources (GIT Summary). Or, to access this tree using git directly, use something like:

git clone git://git.linux-xtensa.org/git/u-boot/u-boot-xtensa.git u-boot

(Note: This path is subject to change.)

Before you can build U-Boot you must have built the toolchain for XTensa core. Set your PATH to point to the toolchain built using buildroot.

  $ export PATH="<workdir>/buildroot/build_xtensa_<cname>/staging_dir/usr/bin:$PATH"

where <cname> is the name of the Xtensa core variant you wish to build for (e.g., dc232b).

To build U-Boot, first clone the tree as above, change to the top level of the tree, then configure it for your board and Xtensa core variant as follows:

make <cname>_<board>_config

This should only take a few seconds. For example, to build U-boot for the 'xtav60' board and 'dc232b' core:

make dc232b_xtav60_config

Only boards and core variants currently supported in the tree can be built out of the box. Headers for supported cores can be found in the tree under include/asm-xtensa/variant-<cname>. The core specific headers are described in the doc/README.xtensa file. To support a new core, these headers must be copied from the overlay in the same way as for the linux kernel.

After the configuration step, to actually build U-Boot, simply:

make all

This will take a few minutes.

Next, start xt-gdb and load u-boot from the top of the git repository:

 cd u-boot-xtensa
 xt-gdb -n
 file u-boot
 target remote localhost:20000 0
 reset
 load
 break panic
 continue

Hopefully u-boot will start and display on the LCD

 U-Boot 50.00 Mhz

Next, set you environment variables to point the the DHCP and TFTP server:

   setenv serverip 192.168.11.78           rtos-lab2
   setenv ipaddr 192.168.11.95             I/P address of host running on the LX60
   setenv bootfile u-boot.bin
   saveenv

Next, download 'u-boot.bin' from the tftp server:

 tftpboot
   TFTP from server 192.168.11.78; our IP address is 192.168.11.95
   Filename 'u-boot.bin'.
   Load address: 0xd2000000
   Loading: T ########
   done
   Bytes transferred = 107592 (1a448 hex)

Note that the image is a bit less than 2 sectors, so turn off protection on the 1st two sectors and erase the current contents:

 protect off F8000000 F801FFFF
       ... done
       Un-Protected 2 sectors

 erase F8000000 F801FFFF
       erase F8000000 F801FFFF
       ... done
       Erased 2 sectors

Now copy the the image of u-boot.bin in memory to the flash:

 cp.b d2000000 F8000000 20000
 Copy to Flash... done

On the LX60 now move DIP switch 8 to the ON position, power cycle the LX60, and you should see U-boot in the LCD display and

 U-Boot 1.3.2 (Aug 27 2009 - 18:23:04)
 
 CPU:    Xtensa dc232b at 50.00 MHz
 Board:  XT-AV60: Avnet board + Xilinx LX60 FPGA + Tensilica bitstream
 SysRAM: 64 MB
 Flash:  4 MB
 In:    serial
 Out:   serial
 Err:   serial
 MAC:
 U-Boot>

Further details on U-Boot in general are in the generic README at the top of the U-Boot tree. Details specific to the Xtensa architecture are in doc/README.xtensa. Details specific to a board are in board[/<family>]/<board>/README (for example board/avnet/xtav60/README).