[yocto] how to tftp download a newer u-boot into RAM and simply execute it?

[Robert P. J. Day]

  ok, i'm trying to do something on my MPC8315E-RDB that *should* be
really simple, and i'm getting nowhere.

  currently on this machine, i have u-boot in NOR flash, and it's old
but it will still boot the other images also stored in NOR flash:

  U-Boot 1.3.0-rc2 (Mar 21 2008 - 16:00:02) MPC83XX

i just built a new image from the current poky repo for precisely
this target, and my generated artifacts include the newer u-boot
binary image:

  -rwxr-xr-x. 2 rpjday rpjday   423964 Jul  5 06:46
	u-boot-mpc8315e-rdb-v2016.03+gitAUTOINC+df61a74e68-r0.bin

rather than immediately write it to flash, i'd like to download and
test it first, and everything i've seen suggests i should be able to:

=> tftp 0x100000 u-boot-mpc8315e-rdb-v2016.03+gitAUTOINC+df61a74e68-r0.bin
=> go 0x100000

  well, the downloading seems to work fine:

=> tftp 0x100000 u-boot-mpc8315e-rdb-v2016.03+gitAUTOINC+df61a74e68-r0.bin
Speed: 1000, full duplex
Using eTSEC0 device
TFTP from server 192.168.1.13; our IP address is 192.168.1.127
Filename 'u-boot-mpc8315e-rdb-v2016.03+gitAUTOINC+df61a74e68-r0.bin'.
Load address: 0x100000
Loading: #############################
done
Bytes transferred = 423964 (6781c hex)
=>

so the number of bytes transferred is correct. and then bad things
happen:

=> go 0x100000
## Starting application at 0x00100000 ...
NIP: 00100008 XER: 20000000 LR: 07FC6614 REGS: 07f2fcd0 TRAP: 0700 DAR: 00000000
MSR: 0008b002 EE: 1 PR: 0 FP: 1 ME: 1 IR/DR: 00

GPR00: 07FC6604 07F2FDC0 00000080 00000001 07F329E4 00000010 00000001 00000030
GPR08: 00000041 00000020 00000006 FFFFFFFF 00000000 00000200 07FF9000 09FB2000
GPR16: 00000000 00000000 00000000 00000000 00000000 FFFFFFFF 00000000 00000000
GPR24: 07F32930 00000000 00000000 00000002 00100000 07F2FF4C 07FF98F8 07F329E4
Call backtrace:
07FC6604 07FD767C 07FD6D10 07FD6E98 07FC6110 07FB6BF8 07FB568C
Program Check Exception
Resetting the board.


  am i missing something? downloading to the wrong address in RAM?
jumping to the wrong entry point? i'mopen to suggestions, i know i've
done this sort of thing before.

  i'm willing to start a new configure and build from scratch if
someone wants to supply a recipe. since this is the current YP powerpc
reference board, it really should work out of the box, no?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================