[PATCH V4] powerpc/85xx: Add machine check handler to fix PCIe erratum on mpc85xx

Scott Wood scottwood at freescale.com
Tue Mar 5 10:45:44 EST 2013

On 03/04/2013 10:16:10 AM, Stuart Yoder wrote:
> On Mon, Mar 4, 2013 at 2:40 AM, Jia Hongtao <B38951 at freescale.com>  
> wrote:
> > A PCIe erratum of mpc85xx may causes a core hang when a link of PCIe
> > goes down. when the link goes down, Non-posted transactions issued
> > via the ATMU requiring completion result in an instruction stall.
> > At the same time a machine-check exception is generated to the core
> > to allow further processing by the handler. We implements the  
> handler
> > which skips the instruction caused the stall.
> Can you explain at a high level how just skipping an instruction  
> solves
> anything?   If you just skip a load/store and continue like nothing is
> wrong, isn't your system possibly in a really bad state.

If the instruction was a load, we probably at least want to fill the  
destination register with 0xffffffff or similar.

> And if the core is already hung, due to the PCI link going down, isn't
> it too late?   How does skipping help?

Maybe the machine check unhangs the core?

Is there an erratum number for this?


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