Question Porting U-Boot to iMX8MN with LPDDR4

[Adam Ford]

I have a board already supported in U-Boot based on the i.MX8MM with
LPDDR4, and with a simple part change, we have built a Nano version as
well with the same LPDDR4.

I have mostly copied the imx8mn EVK files to the board support, and
migrated the device tree files for my board.  I also created a lpddr4
cfg file for the i.MX8MN because it appears to have a different
bootloader than the Mini, but I am referencing the LPDDR4 training
files used on the 8MM.

Unfortunately when I boot, I get a boot-loop with output that looks like this:

U-Boot SPL 2020.07-00499-gd9107930af-dirty (Jul 10 2020 - 09:47:31 -0500)
spl_init
>>SPL: board_init_r()
Normal Boot
WDT:   Started without servicing (60s timeout)
Trying to boot from BOOTROM
image offset 0x8000, pagesize 0x200, ivt offset 0x0
board_fit_config_name_match: imx8mn-beacon-kit
Selecting config 'imx8mn-beacon-kit'outname = uboot at 1
board_fit_config_name_match: imx8mn-beacon-kit
Selecting config 'imx8mn-beacon-kit'outname = fdt at 1
board_fit_config_name_match: imx8mn-beacon-kit
Selecting config 'imx8mn-beacon-kit'outname = atf at 1

U-Boot SPL 2020.07-00499-gd9107930af-dirty (Jul 10 2020 - 09:47:31 -0500)
spl_init
...

I was curious to know if any of the NXP people might have any
suggestions on what I might try.  I have tried building the imx8mn evk
and modifying the Kconfig to reference LPDDR4 instead of DDR4, and
pointing to the cfg file for lpdd4 on the 8mn.  Unfortunately, I don't
see any change.

I have also tried the NXP repos on Code Aurora going to releases as
far back as 4.19_1.10, without success.  I see the standard imx8mn_evk
appears to use lpddr4, but that board doesn't appear upstream.  Does
that board exist?


thanks,

adam