Re: [PATCH 5.3] mt76: mt76x0e: don't use hw encryption for MT7630E

From: Stanislaw Gruszka <sgruszka@redhat.com>
To: Felix Fietkau <nbd@nbd.name>
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Ryder Lee <ryder.lee@mediatek.com>, Roy Luo <royluo@google.com>
Subject: Re: [PATCH 5.3] mt76: mt76x0e: don't use hw encryption for MT7630E
Date: Wed, 21 Aug 2019 13:22:46 +0200	[thread overview]
Message-ID: <20190821112244.GA23546@redhat.com> (raw)
In-Reply-To: <876a4137-ecd5-2e6c-0c75-87eae895e672@nbd.name>

On Wed, Aug 21, 2019 at 12:40:14PM +0200, Felix Fietkau wrote:
> On 2019-08-21 11:03, Felix Fietkau wrote:
> > On 2019-08-21 10:47, Stanislaw Gruszka wrote:
> >> On Tue, Aug 20, 2019 at 01:24:39PM +0200, Stanislaw Gruszka wrote:
> >>> > Can you test if disabling hw encryption only for shared or only for
> >>> > pairwise keys makes any difference?
> >>> 
> >>> Disabling only pairwise keys helps. Disabling only shared keys does
> >>> not help.
> >>> 
> >>> Not sure if this will be helpful information or make things more
> >>> confusing, but seems the difference between mt76_txq_schedule()
> >>> and tasklet_schedule() in mt76_wake_tx_queue() is that on 
> >>> mt76_txq_schedule() some tx packets are serialized by dev->rx_lock
> >>> (because some ARP and TCP packets are sent via network stack as response
> >>> of incoming packet within ieee80211_rx_napi() call). Removing
> >>> spin_lock(&dev->rx_lock) in mt76_rx_complete() make the problem
> >>> reproducible again with mt76_txq_schedule() & HW encryption.
> >> 
> >> So, I think this is FW/HW issue related with encryption and ordering
> >> and we should apply patch originally posted in this thread that
> >> disable HW encryption for MT7630E.
> >> 
> >> I do not think we should disable HW encryption only for pairwise keys,
> >> because FW/HW can have the same bug for shared keys, but is not
> >> triggered in my test, as we do not sent lot of group frames.
> > I'm still not convinced that this is just the hardware implementation of
> > hw crypto being faulty. I think it's more likely that there's a bug in
> > the tx path somewhere, which causes hangs on MT7630E but remains hidden
> > (or at least recoverable) on other devices.
> > I'm currently reviewing key handling in the mac80211 fast-xmit codepath
> > and get the feeling that something might be racy there.
> > I will let you know when I make some progress with that review.
> > If we can't find the bug soon, then I'm fine with merging this patch.
> > Right now, I would like to see first if we can fix it properly.
> Another question: Does a watchdog restart happen before tx fails?

No, we do not run wdt_work for mt76x0e.

Stanislaw