Re: [linuxwifi] [RFC] iwlwifi: enable TX AMPDU for some iwldvm

From: Kevin Locke <kevin@kevinlocke.name>
To: "Grumbach, Emmanuel" <emmanuel.grumbach@intel.com>
Cc: linuxwifi@intel.com, linux-wireless@vger.kernel.org, "Coelho,
	Luciano" <luciano.coelho@intel.com>
Subject: Re: [linuxwifi] [RFC] iwlwifi: enable TX AMPDU for some iwldvm
Date: Tue, 12 Mar 2019 15:44:45 -0600	[thread overview]
Message-ID: <20190312214445.GA20993@kevinolos> (raw)
In-Reply-To: <58bd45ab11912eef5c809427449a31800ecdbf53.camel@intel.com>

On Tue, 2019-03-12 at 20:48 +0000, Grumbach, Emmanuel wrote:
> On Tue, 2019-03-12 at 14:31 -0600, Kevin Locke wrote:
>> On Tue, 2019-03-12 at 19:47 +0000, Grumbach, Emmanuel wrote:
>>> We had issues with reclaim path upon BACK. This is of course a
>>> firmware problem...
>> 
>> Does that suggest the issue may have been fixed by a firmware update?
>> For reference, I'm currently using "firmware version 9.221.4.1 build
>> 25532" from the firmware-iwlwifi Debian package (version 20190114-1).
>> 
>> If it would be helpful, I could attempt to bisect the firmware
>> revisions to find the one that fixed it (assuming I can reproduce the
>> issue with a previous firmware version).
> 
> Well.. Sorry, I wasn't very "technical".
> So the problem was really that we stopped getting BACK notifications
> from the firmware and that caused a reclaim stall which in turn was
> caught by a Tx queue stuck timer firing in the driver.
> I was never able to reproduce this. What I can do is to enable A-MPDU
> on my old system that has this same device, just to see what happens.

Thanks for the additional details and for offering to try it out, that
would be great!

> While chasing this bug, I even found another one which bought me a few
> moments of fame:
> 
> commit d6ee27eb13beab94056e0de52d81220058ca2297
> Author: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
> Date:   Wed Jun 6 09:13:36 2012 +0200
> 
>     iwlwifi: don't mess up the SCD when removing a key
> 
> and in the commit message of that very commit:
> 
>     This doesn't seem to fix the higher queues that get stuck
>     from time to time.
> 
> There were no new versions of the firmware released since then.
> I tried to skim through bugzilla, but couldn't find the bugs I was
> handling then.

Ah.  You are right about the firmware version.  I should have checked.

I see what you mean.  I found several reports for TX queue stuck
issues in Bugzilla.  Perhaps this is one (or one of its many dups):
https://bugzilla.kernel.org/show_bug.cgi?id=56581

Let me know if there is anything I can do to help search or test.

Thanks again,
Kevin