From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Adam Kropelin" <akropel1@rochester.rr.com>
Subject: Re: 2.6.20-rc7: known regressions (v2) (part 1)
Date: Sat, 3 Feb 2007 16:00:02 -0500
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Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	"Adrian Bunk" <bunk@stusta.de>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	<jgarzik@pobox.com>, <alan@lxorguk.ukuu.org.uk>,
	"Allen Parker" <parker@isohunt.com>, <jesse.brandeburg@intel.com>,
	<gregkh@suse.de>, <linux-pci@atrey.karlin.mff.cuni.cz>,
	<netdev@vger.kernel.org>
To: "Auke Kok" <auke-jan.h.kok@intel.com>
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Auke Kok wrote:
> Adam Kropelin wrote:
>> I've never had this device work 100% with MSI on any kernel version
>> I've tested so far. But I'm not the original reporter of the
>> problem, and I believe for him it was a true regression where a
>> previous kernel wored correctly.
>
> maybe I've been unclear, but here's how e1000 detects link changes:
>
> 1) by checking every 2 seconds in the watchdog by reading PHY
> registers

That would explain why I see link status changes but 0 interrupt count 
in /proc/interrupts. However, on >= 2.6.19 the link state never changes. 
Ever. It's always down. On <= 2.6.18 the link state does change but with 
0 interupt count.

> 2) by receiving an interrupt from the NIC with the LSI bit
> in the interrupt control register
>
> if the link is down to start with, the watchdog will obviously spot a
> 'link up' change since it doesn't use any interrupts.

This does not seem to work on 2.6.19+. Unless the watchdog interval is 
tens of minutes. I've waited at least 5 minutes and link never went up.

>> The behavior I observe on 2.6.19 is better than 2.6.20-rc7. Link
>> status interrupts seem to work but rx/tx does not. A few more
>> details here:
> <http://www.kroptech.com/~adk0212/mailimport/showmsg.php?msg_id=3339092450&db_name=linux_kernel>
>
>> I'm going to test 2.6.16 thru 2.6.20-rc7 this weekend and will report
>> back any variations in behavior I notice.
>
> that would be a good start, but I still think that you might have a
> broken bridge on that system. Anyway, thanks for digging into this.

Will continue to dig.

--Adam