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

[Jia Hongtao-B38951]

> -----Original Message-----
> From: David Laight [mailto:David.Laight at ACULAB.COM]
> Sent: Tuesday, March 05, 2013 1:16 AM
> To: Jia Hongtao-B38951; linuxppc-dev at lists.ozlabs.org;
> galak at kernel.crashing.org
> Cc: Wood Scott-B07421
> Subject: RE: [PATCH V4] powerpc/85xx: Add machine check handler to fix
> PCIe erratum on mpc85xx
> 
> > 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.
> 
> Just skipping the instruction doesn't seem a good idea.
> But I suspect that re-initialising the PCI interface is also almost
> impossible.

This *skipping* is the best way I thought for this errata.
It's not perfect but works.

-Hongtao.

> 
> Does the mpc83xx have the same errata?
> We've seen machine-check faults using the CSB bridge on an 83xx doing a
> 'pio' access after a PEX_DMA transfer to certain target addresses stalls
> - software gives up waiting for the dma.
> The target is an fpga, nothing is mapped at those addesses - but we'd
> expect to get ~0u back as happens on other slave windows.
> 
> I also remember some problems with single word DMA.
> 
> 	David
> 
>