TI AM170x Booting Annoyances

Although I haven't spent much time working on the TuxedoBoard in the past few months (newborn daughter in July), I've been thinking about it again recently as my sleep schedule is starting to normalize a bit.

In reading through the info from TI about boot modes on the AM17xx processors, a lot of time is spent describing the AIS (Application Image Script) proprietary boot script system. It's proprietary to TI, the script generator only runs on Windows, and it requires that you pay for and use Code Composer Studio. None of that sounds exciting to someone interested in open platforms.

So, if the AM170x processor is going to go onto the TuxedoBoard, there's going to have to be a custom bootloader.

Ideally, I would want a bootloader that doesn't require an external memory interface (either EMIFA, SPI, or I2C) due to the added cost and complexity. I'm imagining that there will be an MMC/SD card on the TuxedoBoard in order to hold the Linux filesystem, so booting directly off of that would be best. The BeagleBoard-xM boots off the MMC/SD card but its processor has internal firmware (not sure on the details) that is smart enough to find a FAT partition (if its the first one) and grab the MLO (x-loader) file (if its the first file loaded onto the partition).

I'd like it if my bootloader can setup the external SDRAM, set up all registers properly, find the MMC/SD card, transfer uboot (or other second stage bootloader) into RAM and jump to it. Kind of like the BeagleBoard-xM does it. There's 64kB of ROM and 8kB of RAM inside the AM170x ARM core. I'm not sure if that's enough but coming from a 8/16-bit microcontroller perspective, that's decent for doing quite a lot. It seems possible (even if it will be a lot of work).

It'd be awesome if the first partition on the MMC/SD card could be ext2 (or other open and less complex filesystem) and have only the uboot executable. The second partition (in your favorite, supported by uboot, format) would hold the actual Linux filesystem.

UPDATE 1 October 2011: I'm incorrect in some of the things stated in this blog post. I've not changed them but I have written another blog post.