Subject: Board boots when in BDM, hangs otherwise

From: "Joshua Horvath" <[email-masked]>
Date: Mon, 01 May 2000 14:36:32 -0500

I've got a custom 855T based board that I'm having trouble getting Linux to
boot up on consistently.

I've written a simple bootloader that allows me to TFTP an image to RAM and
execute it.  If I download this program via the BDM port and run it, everything
works fine.  The ethernet download works fine and the kernel boots without a
hitch.

I then progammed this code into flash and although everything appears to work
correctly, Linux won't boot after downloading the image to RAM.  I've verified
that the image is in fact uncorrupted after download so I would expect it to
boot correctly.  The bootup goes like this:

loaded at:     00210000 0021C578
relocated to:  00100000 0010C578
board data at: 001001C8 001001E4
relocated to:  00200100 0020011C
zimage at:     00217000 00282603
initrd at:     00282603 00459440
avail ram:     0045A000 01000000

Linux/PPC load:
Uncompressing Linux...done.
Now booting the kernel
Linux version 2.2.13 ([email-masked]) (gcc version 2.95.2 19991024
(
release)) #152 Wed Apr 26 15:22:16 CDT 2000
Boot arguments: root=/dev/ram
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.46 BogoMIPS
clear_bit(0, c01381c0)
NIP: C0007030 XER: E000217F LR: C0007030 REGS: c00dcb50 TRAP: 0300
MSR: 00009032 EE: 1 PR: 0 FP: 0 ME: 1 IR/DR: 11
TASK = c00dac90[0] 'swapper' mm->pgd c00d9000 Last syscall: 0
last math 00000000
GPR00: C0007030 C00DCC00 C00DAC90 0000001A 00000001 00000017 00000000 C00F6849
GPR08: 00000017 C00F0000 FF002808 C00DCB40 95113133 000191B8 00004C00 00000000
GPR16: 00000000 C04DCC00 C00F0000 C0120000 C0120000 00000000 00000000 C015B000
GPR24: C0120760 00000000 C012075C C1000000 C00F0000 00000001 C1000000 00000001
Call backtrace:
C0007030 C00EBC5C C00EA6E4 C000221C
Kernel panic: kernel access of bad area pc c0007030 lr c0007030 address
C1000000
 tsk swapper/0
In swapper task - not syncing
Rebooting in 180 seconds..

I'm using the EST VisionICE box to do the BDM download.  Now, the weird thing
is, if I do an "IN" command (which does some basic initialization and puts the
processor in debug mode) and then jump to flash and execute my code, everything
works fine.  My bootloader code also does board initialization and as far as I
can tell I'm setting up the registers the exact same way, so I can't figure out
what is getting configured differently by the VisionICE box.  I've disabled the
MMU and the caches.

I've also noticed that the code executes faster after I do an "IN" and jump to
flash (i.e. when I'm in BDM) versus when I just powerup or do a hard reset and
have the code execute automatically.

Does anyone know what the problem might be?  Since it runs correctly after
being initialized by the VisionICE box I assume something is wrong with my
hardware init routine but I can't figure out what that is.

Thanks,
-Josh

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