[U-Boot] T1040RDB u-boot chain load u-boot

[Nicolae Rosia]

Hello,

I have a u-boot-with-spl-pbl.bin booting off NAND, and now I would
like to create another build of u-boot to be chain-loaded, and I would
appreciate some assistance.

I'm using u-boot tag v2018.05, config T1040RDB_NAND_defconfig as base.

Here's what I tried

Scenario 1:
Checking the defconfig, I see that CONFIG_SYS_TEXT_BASE=0x30001000, so
I went ahead and tried:
=> tftp 30001000 u-boot.bin
=> go 30001000
## Starting application at 0x30001000 ...
and it hangs

Scenario 2:
Different load address:
=> tftp 1000000 u-boot.bin
=> go 1000000
## Starting application at 0x01000000 ...
hang

Scenario 3:
I was thinking that maybe I need to bump the load and text address by
8MB so it does not matches the currently running u-boot (which has
CONFIG_SYS_TEXT_BASE=0x30001000), so I applied the following patch:
--- a/configs/T1040RDB_NAND_defconfig
+++ b/configs/T1040RDB_NAND_defconfig
-CONFIG_SYS_TEXT_BASE=0x30001000
+CONFIG_SYS_TEXT_BASE=0x30801000

=> tftp 30801000 u-boot.bin
=> go 30801000
same hang
also different address:
=> tftp 1000000 u-boot.bin
=> go 1000000
## Starting application at 0x01000000 ...

Scenario 4:
Remove RAMBOOT_PBL from defconfig:
-CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL"
+CONFIG_SYS_EXTRA_OPTIONS="SPL_FSL_PBL"

This results in a binary that is more than 3GB (??????)

Scenario 4.1:
I noticed that CONFIG_SYS_TEXT_BASE affects the size of binary so I
thought I can fix this by placing it near RAM end, 4 GB - 8 MB:
-CONFIG_SYS_TEXT_BASE=0x30001000
+CONFIG_SYS_TEXT_BASE=0xFF800000
-CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL"
+CONFIG_SYS_EXTRA_OPTIONS="SPL_FSL_PBL"

but the size of u-boot.bin is ~249 MB

I also went through, doc/README.ramboot-ppc85xx which describes what I need.
Looking over ./arch/powerpc/cpu/mpc85xx/start.S, I see that CCSR
relocation is happening but I can't tell to which value, which might
explain why I get hangs.
I'll have to investigate more.

Any ideas are appreciated.

Best regards,
Nicolae