Hello Wolfgang,
On Mon, Jun 20, 2011 at 3:46 PM, Wolfgang Denk wd@denx.de wrote:
Dear Christian Riesch,
In message 1308575272-30559-1-git-send-email-christian.riesch@omicron.at you wrote:
On this board, older versions of u-boot (like v2009.11) boot perfectly, even when TI's UBL boot loader is not used (instead the configuration of DDR memory was done using an AIS script). However, since commit
What is AIS ?
I apologize for using that many abbreviations in my mail and not explaining them :-/
AIS is short for Application Image Script [1]. It is a boot script that is processed by the ROM bootloader on Texas Instrument's AM1808/DA850/OMAP-L138 processors. The script allows configuration of boot modes, PLLs, DDR memory, Pinmuxes etc and loading the an application like u-boot from flash to RAM and executing it. Using a suitable AIS one can configure PLL and DDR memory and then directly start u-boot on these processors, without using Texas Instruments's user boot loader (UBL) [2].
In the default configuration of the da850evm the boot sequence is like this: 1) ROM bootloader (RBL): starts reading from flash 2) In the SPI-flash, a very simple AIS is present. This AIS tells the RBL to load the UBL from flash and to start it. 3) The UBL does a lot of hardware initialization and then loads u-boot from flash and starts it. 4) u-boot does a lot of hardware initialization that has already been done by the UBL and then loads the Linux kernel.
For my application I would like to get rid of the UBL since most of the configuration it does is also done by u-boot (although there seems to be a bug in it) or can be done by AIS (like PLL and DDR memory configuration), the resulting boot sequence will be: 1) ROM bootloader (RBL): starts reading from flash 2) In the SPI-flash, an AIS is present. This AIS tells the RBL to configure PLLs and DDR memory and to load u-boot from flash and to start it. 3) u-boot loads the Linux kernel.
Hope that helps :-) Best regards, Christian
[1] Using the AM18xx Bootloader (Rev. A) http://focus.ti.com/dsp/docs/litabsmultiplefilelist.tsp?sectionId=3&tabI...