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

From: "David Laight" <David.Laight@ACULAB.COM>
To: "Jia Hongtao" <B38951@freescale.com>,
	<linuxppc-dev@lists.ozlabs.org>, <galak@kernel.crashing.org>
Cc: B07421@freescale.com
Subject: RE: [PATCH V4] powerpc/85xx: Add machine check handler to fix PCIe erratum on mpc85xx
Date: Mon, 4 Mar 2013 17:15:42 -0000	[thread overview]
Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B7173@saturn3.aculab.com> (raw)
In-Reply-To: <1362386425-20149-1-git-send-email-B38951@freescale.com>

> 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.

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