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imx6 w/Kernel 3.0.35 for mcfg tools: Unhandled fault: Imprecise External Abort

Question asked by Stephen Dickey on May 15, 2014
Latest reply on May 16, 2014 by Wlodek_D.

I am having a very strange failure on the 3.0.35 kernel.  We have a mostly-identical sister board that has no such fault.


Kernel Revision 3.0.35

Patches Applied (all ltib patches distributed && as many patches up to 3.0.101 as possible)

** it doesn't matter if I'm taking straight 3.0.35 ltib based code or not, no change to the failure ***


Bad Board:

Processor: imx6 solo : MC1MX6S7CVM08AB / XAA1317

DDR3: 3QK17 / D9PSL x 2

DDR3 I/O voltage @ 1.5 volts


Good Board:

Processor: imx6 solo : MC1MX6S7CVM08AB / XAA1350

DDR3: 3UK17 / D9QTF

DDR3 I/O voltage @ 1.35 volts


The failure is:


50] Unhandled fault: imprecise external abort (0x1c06) at 0xf932d7a1.

<0>[    0.092526] Internal error: : 1c06

This is happening just after the kernel attempts to do a __schedule() of the first threads in the system.  It is just after the normal kernel debug line:

"CPU: Testing write buffer coherency: ok."


but I've added debug to get further into the code


__schedule:4293 <<< extra debug to tell me the line number of where I am in __schedule()

<5>[0.092414] Scheduling: swapper <<< extra debug to tell me what thread I am about to schedule, prints out next->comm[] in task structure.

Notice that I'm capturing this from RAM after a restart: there is no serial console or debug output functioning after the kernel boots.

Any thoughts on why this might be happening?  Any and all thoughts are welcome.