linux-kernel - Re: [PATCH] Add EDAC peripheral init functions & Ethernet EDAC.

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Message-ID: <5711087A.8050501@opensource.altera.com>
Date:	Fri, 15 Apr 2016 10:27:54 -0500
From:	Thor Thayer <tthayer@...nsource.altera.com>
To:	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Rob Herring <robh@...nel.org>
CC:	<bp@...en8.de>, <dougthompson@...ssion.com>, <pawel.moll@....com>,
	<mark.rutland@....com>, <ijc+devicetree@...lion.org.uk>,
	<galak@...eaurora.org>, <linux@....linux.org.uk>,
	<dinguyen@...nsource.altera.com>, <grant.likely@...aro.org>,
	<devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<linux-edac@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <tthayer.linux@...il.com>
Subject: Re: [PATCH] Add EDAC peripheral init functions & Ethernet EDAC.



On 04/15/2016 04:40 AM, Mauro Carvalho Chehab wrote:
> Em Thu, 14 Apr 2016 09:35:01 -0500
> Rob Herring <robh@...nel.org> escreveu:
>
>> On Tue, Apr 12, 2016 at 05:12:55PM -0500, tthayer@...nsource.altera.com wrote:
>>> This patch set adds the memory initialization functions for Altera's
>>> Arria10 peripherals, the first of which is the Ethernet EDAC. The
>>> first 3 patches add the memory initialization functionality. The
>>> last 3 patches add Ethernet EDAC support.
>>
>> The ethernet part seems a bit strange to me to put under EDAC as EDAC
>> is primarily memory controller ECC (and caches to some extent). Also you
>> would not halt the system in case of an UC, but rather just drop the
>> frame. This would need to be part of the ethernet driver in that case.
>>
>> Of course, given that ethernet frames already have a CRC, ECC of the
>> FIFO seems a bit redundant.
>
> Actually, EDAC was conceived to be a way to report hardware errors, and,
> although the main use case is for memory and CPU errors, there are a few
> drivers that report errors at PCI bus. So, I don't see much problems using
> it to report other hardware errors, like the ones associated with the
> Ethernet hardware.
>
> That's said, things like Ethernet frame errors are better handled via the
> network drivers. I would report via EDAC only errors associated with the
> Ethernet hardware that would cause the hardware to malfunction.
>
> Btw, an UC error won't cause the system to halt, except if a UC memory
> error happens and the EDAC core is loaded with an special modprobe
> parameter (edac_mc_panic_on_ue = 1).
>
Thank you for the clarification. Rob's comment was logical and made me 
re-think this. He pointed out that I was causing a kernel panic in the 
case of Uncorrectable errors which is not the desired response and will 
need to change.

I'll update this patch to only count errors. I'll need to re-think how 
the network driver can be alerted that there was an uncorrectable error 
but that could be a later patch.

Great feedback. Thank you Mauro and Rob for reviewing and commenting!