netdev - Re: [PATCH] e1000e: MSI interrupt test failed, using legacy interrupt

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Message-ID: <4F9AF8EB.60703@riverbed.com>
Date:	Fri, 27 Apr 2012 12:52:11 -0700
From:	Prasanna Panchamukhi <ppanchamukhi@...erbed.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	bruce.w.allan@...el.com, jeffrey.t.kirsher@...el.com,
	jeffrey.e.pieper@...el.com, gospo@...hat.com, sassmann@...hat.com,
	jesse.brandeburg@...el.com, e1000-devel@...ts.sourceforge.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH] e1000e:  MSI interrupt test failed, using legacy interrupt

On 04/26/2012 06:40 PM, Ben Hutchings wrote:
> On Thu, 2012-04-26 at 17:05 -0700, prasanna.panchamukhi@...erbed.com
> wrote:
>> From: Prasanna S. Panchamukhi<ppanchamukhi@...erbed.com>
>>
>> Following logs where seen on Systems with multiple NICs&  ports,
>> while using MSI interrupts as shown below:
> [...]
>> This patch changes the IRQ tests to use polling loops starting with a
>> delay of 1 tick and doubling that if necessary up to a maximum total
>> delay of approximately 1 second.
> [...]
>
> I don't think you entirely understood my point.  This exponential
> back-off was the best I could come up with for a self-test
> (ethtool -t) where we have to answer the question 'are interrupts
> working' in a reasonable time, and the user can decide for themselves
> whether this was a false negative.
>
> If you want a definite answer in order to make an automatic decision
> about interrupt modes, there really is no valid time limit.  I think the
This issue is not able interrupt mode selection.

-Prasanna
> proper way to do interrupt mode selection in an in-tree driver is to
> rely on no-MSI quirks for chipsets and devices in the PCI core.
>
> Ben.
>

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