netdev - Re: [PATCH] e1000e: test MSI interrupts

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Message-ID: <20080327223337.GP856@gospo.usersys.redhat.com>
Date:	Thu, 27 Mar 2008 18:33:37 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	"Kok, Auke" <auke-jan.h.kok@...el.com>
Cc:	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	Jeff Garzik <jeff@...zik.org>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: Re: [PATCH] e1000e: test MSI interrupts

On Thu, Mar 27, 2008 at 03:16:41PM -0700, Kok, Auke wrote:
> Andy Gospodarek wrote:
> > On Thu, Mar 27, 2008 at 10:53:43AM -0700, Brandeburg, Jesse wrote:
> >> Kok, Auke wrote:
> >>> Jeff Garzik wrote:
> >>>> Auke Kok wrote:
> >>>>> From: Jesse Brandeburg <jesse.brandeburg@...el.com>
> >>>>>
> >>>>> Test the MSI interrupt physically once before assuming that it
> >>>>> actually works. Several platforms have already come across that
> >>>>> have non-functional MSI interrupts and this code will attempt
> >>>>> to detect those safely. Once the test succeeds MSI interrupts
> >>>>> will be enabled.
> >>>>>
> >>>>> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> >>>>> Signed-off-by: Auke Kok <auke-jan.h.kok@...el.com>
> >>>> Ah, the perennial add-same-test-to-every-driver conundrum.
> >>>>
> >>>> I think we are far enough along with MSI to _not_ do this anymore in
> >>>> drivers. 
> >> Actually, I'm hoping you'll allow this Jeff, we have a production system
> >> (see below) we know about that doesn't like the way 82571 formats MSI
> >> interrupt messages.  All other systems seem to be okay with this format
> >> of MSI messages, but this system implemented a stricter interpretation
> >> of the spec, and so even though that system doesn't need a quirk for MSI
> >> because MSI works in general, we still MUST test the MSI vector to make
> >> sure it works *for us*  In this case it comes down to being an errata
> >> workaround.
> >>
> >> Since there is no way to "test" generation of an interrupt from any
> >> specific hardware device without internal knowledge of said device,
> >> there isn't a way for us to help the kernel by writing a generic "test
> >> MSI" routine.
> >>
> >> I would prefer this "generic test" code be in the driver rather than
> >> having to identify all the chipsets that fail and have the driver do
> >> *specific chipset* detection ala bnx2.c's 8132 bridge workaround.
> >>
> >>>> The platforms with MSI problems should be discovered, made public,
> >>>> and worked around. 
> >> This is our workaround, it is our fault, the incompatible chipset is in
> >> an x3850 IBM system.
> >>
> > 
> > I've seem similar problems on other systems, so this would be a nice bit
> > of code to have somewhere.  I can see Jeff's argument for having this
> > outside of drivers, but to make my life easier I'd like to see this in
> > e1000e (and e1000!).  :-)
> 
> e1000 will soon no longer support PCI Express devices, so this is unneeded.
> 

So you plan to drop the bits around the device additions that are
related to e1000e config sometime soon?
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