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

[Ben Hutchings <bhutchings@solarflare.com>]

On Thu, 2012-04-26 at 17:05 -0700, prasanna.panchamukhi@riverbed.com
wrote:
> From: Prasanna S. Panchamukhi <ppanchamukhi@riverbed.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
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.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.


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