From: Simon Wunderlich <sw@simonwunderlich.de>
To: Felix Fietkau <nbd@nbd.name>
Cc: linux-wireless@vger.kernel.org, kvalo@codeaurora.org
Subject: Re: [PATCH 3/4] ath9k: check for deaf rx path state
Date: Thu, 26 Jan 2017 11:15:00 +0100 [thread overview]
Message-ID: <2448336.mzt5URIzpg@prime> (raw)
In-Reply-To: <809a5011-4361-0459-2937-5dd5b0d619c2@nbd.name>
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Hey,
On Thursday, January 26, 2017 11:02:53 AM CET Felix Fietkau wrote:
> On 2017-01-26 10:50, Simon Wunderlich wrote:
> > Hey Felix,
> >
> > On Wednesday, January 25, 2017 5:36:53 PM CET Felix Fietkau wrote:
> >> Various chips occasionally run into a state where the tx path still
> >> appears to be working normally, but the rx path is deaf.
> >>
> >> There is no known register signature to check for this state explicitly,
> >> so use the lack of rx interrupts as an indicator.
> >>
> >> This detection is prone to false positives, since a device could also
> >> simply be in an environment where there are no frames on the air.
> >> However, in this case doing a reset should be harmless since it's
> >> obviously not interrupting any real activity. To avoid confusion, call
> >> the reset counters in this case "Rx path inactive" instead of something
> >> like "Rx path deaf", since it may not be an indication of a real
> >> hardware failure.
> >>
> >> Signed-off-by: Felix Fietkau <nbd@nbd.name>
> >
> > As we observed in the field, it may happen that there are still RX
> > interrupts triggered, but just a very low number - in which case I
> > believe your version wouldn't fix the problem. Therefore we had a
> > threshold in our original patch [1].
>
> It seems that you were seeing something different than what I was seeing
> in my tests. Though it could be that my issues were actually caused by
> something else. I had queued up these changes a while back before I
> finally found and fixed the IRQ issue.
What we found a good threshold was to check for less than 1 RX interrupt per
second, and check the mean average (about) every 30 seconds. If there is any
other AP or a station connected, it will not reset the chip, and also there
will be no reset on short outages.
However, Access Points "alone" somewhere without users may still accumulate a
lot of false resets. Your name choice is better than ours in this regard, lets
hope users understand that as well. :)
>
> > We would also appreciate if you can at least briefly mention our work if
> > you resend/rework our stuff.
>
> Sorry about that. I rebased this from older experimental patches and
> forgot to put in all the relevant context.
Cool, thanks!
Simon
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next prev parent reply other threads:[~2017-01-26 10:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-25 16:36 [PATCH 1/4] ath9k: rename tx_complete_work to hw_check_work Felix Fietkau
2017-01-25 16:36 ` [PATCH 2/4] ath9k_hw: check if the chip failed to wake up Felix Fietkau
2017-01-25 16:36 ` [PATCH 3/4] ath9k: check for deaf rx path state Felix Fietkau
2017-01-26 9:50 ` Simon Wunderlich
2017-01-26 10:02 ` Felix Fietkau
2017-01-26 10:15 ` Simon Wunderlich [this message]
2017-01-26 10:26 ` Felix Fietkau
2017-01-26 10:32 ` Simon Wunderlich
2017-01-25 16:36 ` [PATCH 4/4] ath9k: fix race condition in enabling/disabling IRQs Felix Fietkau
2017-01-27 12:47 ` Felix Fietkau
2017-02-02 9:10 ` Kalle Valo
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