[U-Boot] [PATCH 6/6] RFC: am335x: enable falcon boot mode for mmc (raw and fat)

[Peter Korsgaard]

>>>>> "Tom" == Tom Rini <trini at ti.com> writes:

Hi,

 >> Yes, I did. I'm personally most interested in raw mode because of
 >> the 4x redundant MLO handling.

 Tom> Note that you only get 3 on RAW mode because we place U-Boot (by
 Tom> default) in the fourth slot.  I noticed this recently but was hesitant
 Tom> to break possible deployed setups (in beagle land).  RAW mode isnt' well
 Tom> documented, but it is in a few places.  For your device I imagine you
 Tom> could fix things however.

And you possibly lose the first if you need a DOS style MBR, but that's
OK, I just want to be able to field upgrade the MLO without risks, so 2
is enough.


 >> No particular reason, 0x700 should work as well. As mentioned, this was
 >> just a proof of concept to be able to test it.

 Tom> Right.  And I'd love to see bootcount or similar updated so that
 Tom> we can try redundant copies of U-Boot.

Me too. I'll do some work on it in the relatively near future. I haven't
looked enough into it yet to know if bootcount is enough, or if I would
need custom SPL logic (basically a platform specific spl board_init_r).

The behaviour I would like to have is:

- eMMC split in two parts, and everything (u-boot/linux/rootfs) doubled

- SPL reads a flag somewhere (probably a raw eMMC sector) to decide if
  it should boot low or high uImage / u-boot

- On error (reset because of watchdog, bootcount, ..?) it falls back to
  the other part

- On upgrades the currently unused part is written and the boot flag
  changed.

That's AFAIK currently not possible to do with SPL, as the boot
addresses are build time defines.


 >> I can try to come up with sensible NAND values, but I don't have a EVM
 >> to test.

 Tom> Well, CONFIG_SYS_NAND_SPL_KERNEL_OFFS would be where we say nandimgsrc
 Tom> is in env.  Stefano, looking at twister, the spl export looks like it
 Tom> goes right at the start of the rootfs, isn't that bad?  Or at least,
 Tom> luck?

You mean nandsrcaddr, right? CONFIG_CMD_SPL_NAND_OFS just need to be
somewhere unused on the nand.

-- 
Bye, Peter Korsgaard