Question Porting U-Boot to iMX8MN with LPDDR4

[Peng Fan]

Sorry for top post and not plain text. connection issue with O365.

To JTAG to see whether DRAM is stable.
Fire a breakpoint or deadloop in the end of SPL, or beginning of ATF to narrow down which triggers reboot.
Yes i.MX8MN has LPDDR version, not upstreamed. Did you try NXP 5.4 Q2 release? 4.19 is a bit old.

THanks,
Peng.

________________________________
From: Adam Ford <aford173 at gmail.com>
Sent: Friday, July 10, 2020 10:56 PM
To: U-Boot Mailing List <u-boot at lists.denx.de>; dl-linux-imx <linux-imx at nxp.com>; Peng Fan <peng.fan at nxp.com>
Subject: Question Porting U-Boot to iMX8MN with LPDDR4

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