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

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Message-ID: <47EC2400.50602@intel.com>
Date:	Thu, 27 Mar 2008 15:47:28 -0700
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	Andy Gospodarek <andy@...yhouse.net>
CC:	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	"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

Andy Gospodarek wrote:
> 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?

yes I was hoping to do this for 2.6.26 already, if not 2.6.27.

I definately don't want to have that linger.

Auke

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