USB boot with AM335x, U-boot, looking for information on what code runs in SPL

utelia

Other Parts Discussed in Thread: UNIFLASH

Hello,

I am looking into ways of flashing a custom AM335x board, although currently running on BBB. With Uniflash running the TFTP server, I am now able to boot from USB. The next step would be to make this code which I can boot from USB, to do many of the same steps U-boot does when retrieving the next phase of the code over USB (which will then load the debrick.scr etc.). Unfortuntely, I cannot go to Linux so u-boot itself is out of question.

To accelerate my evaluation and investigation:

Would you be able to give me some insight into what parts of the u-boot code will compile to u-boot.img (aka u-boot-restore.img) and which code to spl/u-boot.bin (u-boot-spl-restore.bin)?

Would you by chance have compiled images (with symbolic information) for the two u-boot images (AM335x, BBB), which I could run (with an emulator) and see for myself which code (especially) the SPL runs to get going with the UBOOT image loading over USB? (This is the only part I am currently missing from my project).

Thanks!

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

SPL is the primary bootloader. It runs in internal RAM, therefore its size is limited below 128kB, and it's primary function is to initialize DDR memory, load u-boot in it and transfer execution to u-boot. I will ask somebody from the SW guys to add more information here.

0 utelia over 9 years ago in reply to Biser Gatchev-XID

Intellectual 290 points

I am looking forward to that information. Understanding where I can see the code doing what you list, is exactly the information which I need, and I will be thankful for getting a headstart in developing my simplified solution.

0 Biser Gatchev-XID over 9 years ago in reply to utelia

TI__Guru**** 393215 points

Are you going for an OS-less solution? Then the Starterware bootloader might be more suitable for you (http://processors.wiki.ti.com/index.php/StarterWare ).

0 utelia over 9 years ago in reply to Biser Gatchev-XID

Intellectual 290 points

Until now, I have been flashing with a CCS-based solution, and booting up from SPI Flash memory. For the SPI Flash Boot, I am using a bootloader which is modified from the StarterWare example. However, that is for a slightly different purpose. (While perfectly good in r&d phase, it will not be good for production).

From the CCS Flashing and SPI (StarterWare) Bootloader, I do have all the bits and pieces for USB based flashing except the steps in SPL, and what I am now looking for is an understanding of what code from the u-boot system it actually runs.

0 utelia over 9 years ago in reply to utelia

Intellectual 290 points

Just a quick remark here: I discovered the doc/README.SPL which appears to point me to right direction. Any clarifying information is still welcome.

0 Ivan Matrakov over 9 years ago in reply to utelia

TI__Expert 4475 points

Hi,

To understand which files are using for SPL and u-boot you have to see in a root directory Makefile, config.mk. Also in a doc/README.SPL have a useful informations.

BR
Ivan

0 Yordan Kovachev over 9 years ago in reply to Ivan Matrakov

TI__Guru**** 161600 points

Hi Utelia,

You can check the makefile, sources & object files (generated after building u-boot) located in ti-sdk-am335x-evm-07.00.00.00/board-support/u-boot-2013.10-ti2013.12.01/spl directory.

Also in OMAP4 devices, sources were separately build (the term there was x-loader):
git clone git://git.omapzoom.org/repo/x-loader.git x-loader
cd x-loader
git checkout dd88047040dce4a926a6ab80e207bc757f44d648
You can check the sources downloaded from the above repo.. it is quite similar in Sitara devices.

Best Regards,
Yordan

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USB boot with AM335x, U-boot, looking for information on what code runs in SPL