EBC Exercise 25 Configuring U-boot

This follows the approach taken in EBC Exercise 13 Configuring the Kernel. We'll use bitbake to get the source files for U-boot and then we'll edit them.

bitbake
When you did EBC Exercise 22 Cross-Compiling and Finding the Right Kernel u-boot was downloaded and compiled. If you used the default configure, the source code was removed once it was done. Check and see:

host$ cd ~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/ host$ ls

You should see a directory starting with. The rest of the name tells what version you have. Change to that directory and see what's there:

host$ cd u-boot-* host$ ls

If you see a git directory, you are in luck. If you see just a temp directory you need to go back to EBC Exercise 22 Cross-Compiling and Finding the Right Kernel and get it installed.

Once you have the git directory, cd to it and look around.

Compiling U-boot
You can now compile U-boot.

host$ source ~/.oe/crossCompileEnv.sh host$ make host$ scp u-boot.bin root@beagle:.

On the beagle, first be sure the FAT partition is mounted beagle$ cd /media/ beagle$ mkdir mmcblk0p1 beagle$ mount /dev/mmcblk0p1 mmcblk0p1/ beagle$ cd mmcblk0p1/ beagle$ ls -ls total 354 2 drwxr-xr-x 4 root root  2048 May 16 15:29 Docs 2 drwxr-xr-x 5 root root  2048 May 16 15:29 Drivers 6 -rwxr-xr-x 1 root root  5829 Aug 14 10:10 LICENSE.txt 84 -rwxr-xr-x 1 root root 85058 Aug 14 08:19 MLO 14 -rwxr-xr-x 1 root root 13976 Aug 14 10:10 README.htm 2 -rwxr-xr-x 1 root root    27 Aug 14 10:23 Uenv.txt 2 -rwxr-xr-x 1 root root   178 Aug 14 10:10 autorun.inf 2 -rwxr-xr-x 1 root root   171 Aug 14 10:10 info.txt 238 -rwxr-xr-x 1 root root 241948 Aug 14 08:19 u-boot.img 2 -rwxr-xr-x 1 root root    33 Aug 14 10:23 uEnv.txt.orig

Make a backup of the original u-boot. beagle$ cp u-boot.bin u-boot.bin.orig beagle$ cp ~/u-boot.bin . beagle$ shutdown -r now

You should now be running the new u-boot.

Assignment

 * 1) Modify u-boot to include your initials in the prompt. (Hint:  Look for the omap3_beagle.h file for the xM or am335x_evm.h for the bone.)
 * 2) Learn what is done when the boot command in entered in u-boot.
 * 3) Find where the code for boot is defined in the u-boot source.

Hint: u-boot# help boot boot - boot default, i.e., run 'bootcmd' Usage: boot u-boot# print bootcmd bootcmd=if mmc rescan ${mmcdev}; then if userbutton; then setenv bootenv user.txt;fi;echo SD/MMC found on device ${mmcdev};if run loadbootenv; then echo Loaded environment from ${bootenv};run importbootenv;fi;if test -n $uenvcmd; then echo Running uenvcmd ...;run uenvcmd;fi;if run loaduimage; then run mmcboot;fi;fi;run nandboot;