IP30: SMP, Almost there?

[Joshua Kinard <kumba@gentoo.org>]

So I've gotten the second CPU in Octane to "tick" again...somehow.  I am
certain someone's cat went missing in the process...

Anyways, it's booting into an initramfs and dying almost immediately with
errors from do_page_fault:

[   15.631359] do_page_fault(): sending SIGSEGV to init for invalid write
access to 0000000000000338
[   15.631395] epc = 0000000000478474 in busybox[400000+110000]
[   15.631408] ra  = 000000000047843c in busybox[400000+110000]

Segmentation fau[   17.399304] Instruction bus error, epc == 000000000041c000,
ra == 000000000041c5c8
lt
[   17.442702] Kernel panic - not syncing: Attempted to kill init!
exitcode=0x0000000a
[   17.442702]
[   17.470272] ---[ end Kernel panic - not syncing: Attempted to kill init!
exitcode=0x0000000a


So after some digging around, I found this thread from way back in 2006 that
seems almost identical:
http://www.linux-mips.org/archives/linux-mips/2006-09/msg00169.html

However, none of the stuff regarding flush_icache_range seems to be around nor
relevant anymore.  But I did comment out one of the #if 0's in
arch/mips/mm/fault.c and got this output:
[   16.755572] Cpu0[init:1:0000000000520378:1:a800000020360bfc]
[   16.772869] Cpu0[init:1:000000007ff45fb0:1:a80000002001cec4]
[   16.790102] Cpu0[init:1:0000000000400160:0:0000000000400160]
[   16.807563] Cpu0[init:1:000000000041c000:0:000000000041c000]
[   16.825027] Cpu0[init:1:0000000000521ff8:1:0000000000402380]
[   16.842141] Cpu0[init:1:0000000000522010:1:00000000004023d8]
[   16.859289] Cpu0[init:1:0000000000422a6c:0:0000000000422a6c]
[   16.876768] Cpu0[init:1:000000000051fffc:0:0000000000400320]
[   16.893915] Cpu0[init:1:00000000004ddaf4:0:00000000004ddaf4]
[   16.911389] Cpu0[init:1:000000000094d008:1:000000000040519c]
[   16.928527] Cpu0[init:1:00000000004e7d9b:0:0000000000404aec]
[   16.946000] Cpu0[init:1:0000000000503cde:0:0000000000428994]
[   16.963441] Cpu0[init:1:000000000047f2d4:0:000000000047f2d4]
[   16.980945] Cpu0[init:1:00000000004f76e8:0:000000000047f380]
[   16.998410] Cpu0[init:1:000000000094eff8:1:00000000004051a0]
[   17.015596] Cpu0[init:1:000000007ff449c8:0:a80000002001d668]
[   17.032716] Cpu0[init:1:000000007ff449d0:1:a800000020360a48]
[   17.050655] Cpu0[init:1:000000000094fff8:1:00000000004051a0]
[   17.068127] Cpu0[init:1:0000000000950ff8:1:00000000004051a0]
[   17.085615] Cpu0[init:1:0000000000952ff8:1:00000000004051a0]
[   17.102741] Cpu0[init:1:0000000000951000:1:0000000000472fc8]
[   17.121391] Cpu0[init:1:0000000000953ff8:1:00000000004051a0]
[   17.138756] Cpu0[init:1:0000000000954ff8:1:00000000004051a0]
[   17.156542] Cpu0[init:1:000000007ff44de8:1:0000000000403398]
[   15.613954] Cpu1[init:75:000000000040c1a0:0:000000000040c1a0]
[   15.614065] Cpu1[init:75:000000007ff44de8:1:0000000000403398]
[   15.631203] Cpu1[init:75:0000000000413b58:0:0000000000413b58]
[   15.631276] Cpu1[init:75:000000000047843c:0:000000000047843c]
[   15.631336] Cpu1[init:75:0000000000000338:1:0000000000478474]

The invalid address (I believe what is effectively a NULL) of
0x0000000000000338 is pretty consistent with the netboot.  Sometimes I get a
panic in a mutex*slowpath function (I forget which one).  But it's way more
predictable with this netboot than with the disks inserted.

Any ideas where to start looking?

--J