Boot iMX6 from IRAM on new Variscite SOM

[Sascha Hauer]

Hi Michael,

On Mon, Jun 13, 2016 at 06:38:31PM -0400, Michael D. Burkey wrote:
> I have already spoken with Sascha about this a bit, but figured I'd
> throw it out here in case anyone had any suggestions.
> 
> Specifically, I'm updating the support for the Variscite SOM to handle
> the newest version of their SOM -- which now includes an EEPROM that
> contains a "DCD-like" script for configuring the DDR3 timing
> parameters.
> 
> Essentially this means that I have to follow a boot procedure similar
> to that used by the current Wandboard setup, which loads part of
> barebox into IRAM/OCRAM on the iMX6, read/configures the DDR3 timings,
> then reloads barebox into DDR3 and starts it.
> 
> I think I have gotten things more or less setup at this point and have
> copied the setup from the Wandboard, but am having trouble getting
> things to actually start from the internal RAM on the board.
> 
> For now, I have a correct DCD already built-in that preconfigures DDR3
> "just in case" and if I set the load address to be DDR3, then
> everything starts up as normal -- which in and of itself points to a
> problem.
> 
> My suspicion is that the boot ROM is still trying to load the full
> image rather than just part of it -- which means that, when I point it
> to the IRAM/OCRAM, it is writing to the aliased memory regions of the
> built in RAM and overwriting itself in the process.
> 
> What/where actually controls the length of the code that gets
> automatically loaded by the iMX6 internal boot ROM and what needs to
> be updated?

Your image name should end with .imx-sram-img, see images/Makefile.imx:

FILE_barebox-imx6-wandboard.img = start_imx6_wandboard.imx-sram-img

Sascha

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