Das U-Boot für das Zipit Z2

Without further adieu from me to you, Das U-Boot for the Z2! Z2 U-Boot

For the most part U-Boot works and can be flashed without much worry, unlike in the recent past. SDHC is now supported. There's still issues when trying to flash from a stock Zipit to U-Boot, so this guide is for a Zipit that has already been flashed to run the 2.6.29 kernel (ie you're already running z2buntu, rootnexus, sidetrack, debian, etc).

An item of note: After U-Boot is installed, there is no longer a way to "shutdown" the Zipit. It can only be suspended or rebooted. Install pm-utils (sudo apt-get install pm-utils) and run sudo pm-suspend to put the Zipit in suspend mode. There are some people working on getting the Zipit to enter "deep sleep" when you halt the system, but this is still in the testing phase.

First, here's a little U-Boot info. The full featured U-Boot bootloader replaces the original Z2's blob bootloader. With U-Boot, you can run scripts at boot time that check for and run applications, kernels, etc from locations in flash or an SD card. Geordy has already played around with the scripts to allow booting the sidetrack userland. U-Boot first tries to load it's environment from flash (0x40000-0x60000 a.k.a. mtdblock1). If there's no environment there or it's corrupted, it uses the default environment.

The default U-Boot environment first looks for an SD card with a FAT partition1 that contains "uboot.script" and runs it. If that is not available, it tries to boot whatever is in flash at 0x60000 (aka mtdblock2).

The environment I've included first looks for an SD card with an ext partition1 that contains "/boot/uboot.script" and runs it. If that is not available, it looks for the FAT partition1 containing "uboot.script". If neither are found, it resorts to booting from flash at 0x60000.

Now, on to the flashing process. Again, this will only work if you have flashed from the stock app to the 2.6.29 kernel.

U-Boot Loading If you would like to keep your current rootfs it's easiest to prepare it for uboot and flash from it. First, you should fix any errors on your current rootfs so it can boot properly. On a Linux PC, run fsck -y /dev/YOURDEVICE, where YOURDEVICE is the correct partition on your SD card. Next, download and extract the uflasher tarball on your Zipit. Next, download the 2.6.35 kernel to your Zipit. Extract the kernel tarball as root to the root directory of your Zipit.

tar -pxvf /path/to/z2-2.6.35-rc3_07162010_modular.tar.bz2 /

That puts the modules in /lib and puts the kernel and uboot.script in /boot. Now, make sure you are not running X, then move to the uflasher folder and run the flash.sh script as root. This walks you through the flashing process. After the flashing is complete, power down your Zipit (remove AC and battery). After you plugin your Zipit you should see the U-Boot console rotated 90 degrees. Support for splash screens is built into this version of U-Boot but I have not tested it. A splash screen would look much better than the rotated U-Boot console.

You can also flash to U-Boot by downloading my base z2buntu with u-boot flasher tarball or image file. This can be copied to an SD card and be booted from a 2.6.29 Zipit or a ubooted Zipit. It contains a VERY basic Ubuntu rootfs and the uflasher script. At the login prompt, enter user and ubuntu for the username/password, respectively. Then follow the motd instructions to start the flash script.
Linux Kernel
Thanks to Marex for porting and compiling U-Boot for the Z2, getting the Zipit code in the mainline kernel, and creating the flash script. Thanks to Marshall for hosting some files. Thanks to gpsfan for figuring out all the USB host goodness. Thanks to rkdavis for bricking one of his Z2's for the team and his overall help. Thanks to Geordy and ssieb for taking the plunge (shortly after me) to U-Boot.