can't access memory above 496M

Rossetti, Alan Alan.Rossetti at
Wed Oct 7 02:43:16 EST 2009

We have an embedded prouct using 8270 based on pq2fads with MontaVista 4.0.1, kernel 2.6.10. We recently had a need to increase memory. We can populate 1x256M, 2x256M, 1x512M or 2X512M. In all configurations with at least 512M, it we set memory size to 496M or greater system crashes on boot up while populating rootfs. With memory size set to <496M system boots and runs fine. U-boot can see and access/test all memory.

Manual says alignment exception can also be due to crossing segment or BAT boundary. BATs look OK, configured as 256M blocks.

Any thoughts would be appreciated.

desched thread 0 started up.
Machine check in kernel mode.
Caused by (from SRR1=49030): Transfer error ack signal
Oops: machine check, sig: 7 [#1]

NIP: C0008680 LR: C0004FAC SP: C0971C80 REGS: c0971bd0 TRAP: 0200    Not tainted
MSR: 00049030 EE: 1 PR: 0 FP: 0 ME: 1 IR/DR: 11

TASK = c0944ab0[1] 'swapper' THREAD: c0970000
Last syscall: 120
GPR00: 00000000 C0971C80 C0944AB0 EEC00000 EEC00000 00017C0B EEBFFFFC 00000004
GPR08: 0000007C 00000000 0000005F 00000000 00944C80 FFFE7DFF C093882C FFFFFFFF
GPR16: C01D3D84 C094C9E0 0009E000 004197FF 00001000 00000000 0009E000 C0971DCC
GPR24: 00000000 FF777000 0000000B 00000000 00000000 C0220000 C0971CD0 00000000
NIP [c0008680] fix_alignment+0x1e4/0x4bc
LR [c0004fac] AlignmentException+0x18/0xb4
Call backtrace:
 c0004fac AlignmentException+0x18/0xb4
 c0004648 ret_from_except_full+0x0/0x4c
 c000d340 __copy_tofrom_user+0xa8/0x234
 c0034f60 __generic_file_aio_write_nolock+0x280/0x4a4
 c0035200 __generic_file_write_nolock+0x7c/0xc4
 c003541c generic_file_write+0x58/0x17c
 c004e48c vfs_write+0x9c/0x11c
 c004e5e8 sys_write+0x4c/0x90
 c0202610 populate_rootfs+0x12c/0x1a4
 c0003a7c init+0x34/0x2b4
 c0006684 kernel_thread+0x44/0x60

Kernel panic - not syncing: Attempted to kill init!

Al Rossetti
Staff Engineer
Tellabs Operations, Inc.
E-Mail: arossett at<mailto:arossett at>

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