IMX8MM 4GiB boundary issue

[Tim Harvey]

Greetings,

I'm working with an IMX8MM board that has 4GiB of DRAM. I've found
that in this configuration the MMC driver and FEC network driver
appear to have some issues with crossing the 4GiB address space. If I
tell U-Boot I have 3GiB everything is ok, but when I set it to 4GiB I
see the following:

MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... Error found for upper 32 bits
Error found for upper 32 bits
Error found for upper 32 bits
*** Warning - No block device, using default environment

In:    serial
Out:   serial
Err:   serial
Net:   DP83867
Warning: ethernet at 30be0000 (eth0) using random MAC address - ea:22:3a:4d:8f:d5
eth0: ethernet at 30be0000 [PRIME]
Hit any key to stop autoboot:  0

On the FEC ethernet side I don't see any errors reported but ping's
fail with 4GiB DRAM.

I suspect drivers have 32bit addressing issues as the base of mem for
IMX8MM is 1GiB so anything over 3GiB of DRAM runs you over the 32bit
boundary.

Anyone run into this yet?

Marek, I noticed you are the maintainer for the technexion pico-imx8mq
which has support for 1, 2, 3, and 4 GiB DRAM. Did you encounter such
issues on the 4GiB variant?

Best Regards,

Tim