netdev - Re: [net-next 5/9] e1000e: Disable ASPM L1 on 82574

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Date:	Thu, 03 May 2012 21:17:04 +0100
From:	Nix <nix@...eri.org.uk>
To:	"Wyborny\, Carolyn" <carolyn.wyborny@...el.com>
Cc:	"Kirsher\, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"davem\@davemloft.net" <davem@...emloft.net>,
	Chris Boot <bootc@...tc.net>,
	"netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
	"gospo\@redhat.com" <gospo@...hat.com>,
	"sassmann\@redhat.com" <sassmann@...hat.com>
Subject: Re: [net-next 5/9] e1000e: Disable ASPM L1 on 82574

On 3 May 2012, Carolyn Wyborny told this:

> It would be good to know why/how your system is re-enabling the
> setting. The problem is not solvable in firmware unfortunately and is
> somewhat platform dependent. MMIO-tracer might be used to try and see

I entirely forgot about that tool! *Definitely* worth trying.

I'll give it a try this weekend.

> when the re-enabling config space is written, but it might be too
> heavyweight for a live production system.

Given that the re-enabling happens at around the same time as the boot
scripts finish running (it's done by the time I can log in), that's not
going to be a problem. Hence my speculation that it's being re-enabled
when the interface stabilizes (which is, of course, asynchronous) or
something like that.

> I am also working on a patch to the driver to detect the condition and
> then do a slot reset to avoid a whole system reboot. Would you be
> willing to test it in your problem system?

Yes, definitely. The whole-system reboot is irritating because the
system is headless, and with its NICs dead that means a big red switch
to reboot when this problem strikes, which gives me the heebie-jeebies
:)

(Turning off ASPM definitely completely fixes it, so it *is* this bug.
It's just getting the disabling to stick that's proving tricky.)

-- 
NULL && (void)
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