Dear Tom,
In message 20190312173125.GP4690@bill-the-cat you wrote:
I think you were misled by Heiko's description. What he really ment was just that the addresses where the boot ROM stored the information about the boot device etc. gets overwriteen when the SPL
For clarity, that's not _quite_ it. The ROM passes the value in a register and we move that to scratch space, see arch/arm/mach-omap2/lowlevel_init.S and save_boot_params. This is done on every 32bit Cortex-A TI platform.
...
OK, but here's the problem. We define off, iirc, 1KiB of that SRAM space as not-stack but scratch space to store stuff in. The first problem you will hit, if something else touches that scratch space is what Heiko found, the boot value got blown away.
I see. Well, I think it's best if Heiko explains in detail; what he has observed, and what when which part of the information got lost. I was just interpreting his mail, so I may easily have misunderstood this.
@ Heiko: Can you please elucidate?
I agree here. Fixing things up such that we can pass things we know =66rom one stage to another in a defined manner, rather than ad-hoc manner, is good. We could even, probably, re-work most of that use of scratch space to be done in another way, or make it safe to re-use later.
Thanks a lot! Let's go for it.
Best regards,
Wolfgang Denk