From: Stanislaw Gruszka <sgruszka@redhat.com>
To: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc: linux-wireless@vger.kernel.org, Felix Fietkau <nbd@nbd.name>,
Ryder Lee <ryder.lee@mediatek.com>, Roy Luo <royluo@google.com>
Subject: Re: [RFC] mt76: fix tx hung regression on MT7630E
Date: Tue, 30 Jul 2019 15:54:51 +0200 [thread overview]
Message-ID: <20190730135450.GA2361@redhat.com> (raw)
In-Reply-To: <20190729140241.GC4030@localhost.localdomain>
On Mon, Jul 29, 2019 at 04:02:41PM +0200, Lorenzo Bianconi wrote:
> > On Fri, Jul 26, 2019 at 02:10:56PM +0200, Stanislaw Gruszka wrote:
> > > Since 41634aa8d6db ("mt76: only schedule txqs from the tx tasklet")
> > > I can observe firmware hangs on MT7630E on station mode: tx stop
> > > functioning after minor activity (rx keep working) and on module
> > > unload device fail to stop with messages:
> > >
> > > [ 5446.141413] mt76x0e 0000:06:00.0: TX DMA did not stop
> > > [ 5449.176764] mt76x0e 0000:06:00.0: TX DMA did not stop
> > >
> > > Loading module again results in failure to associate with AP.
> > > Only machine power off / power on cycle can make device work again.
> > >
> > > I have no idea why the commit caused F/W hangs. Most likely some proper
> > > fix is needed of changing registers programming (or assuring proper order
> > > of actions), but so far I can not came up with any better fix than
> > > a partial revert of 41634aa8d6db.
> >
> > The difference is that with 41634aa8d6db we can run mt76x02_poll_tx()
> > and mt76x02_tx_tasklet() in parallel on 2 different CPUs. Without
> > the commit, since tasklet is not scheduled from mt76_wake_tx_queue(),
> > it does not happen.
> >
> > I'm not quite sure why, but MT7630E does not like when we poll tx status
> > on 2 cpus at once. Change like below:
>
> Hi Stanislaw,
Hi
> have you tried to look at the commit: 6fe533378795f87
> ("mt76: mt76x02: remove irqsave/restore in locking for tx status fifo")?
> Could it be a race between a registermap update and a stats load? (we are using a
> different lock now)
This commit seems to be fine, reverting it did not solve the issue.
> > diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c b/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c
> > index 467b28379870..622251faa415 100644
> > --- a/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c
> > +++ b/drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c
> > @@ -170,7 +170,7 @@ static int mt76x02_poll_tx(struct napi_struct *napi, int budget)
> > mt76.tx_napi);
> > int i;
> >
> > - mt76x02_mac_poll_tx_status(dev, false);
> > + mt76x02_mac_poll_tx_status(dev, true);
>
> I am not sure if we really need mt76x02_mac_poll_tx_status() here since we run
> it in mt76x02_tx_complete_skb() and in mt76x02_tx_tasklet(). Anyway the only
> difference doing so is we do not run mt76x02_send_tx_status().
I thought this is the problem, but it was my mistake during testing.
I tested the above change together with mt76_txq_schedule(dev, txq->ac)
change and get wrong impression it fixes the issue. But above change
alone does not help.
I tried to add some locking to avoid parallel execution of mt76x02_poll_tx()
and mt76x02_tx_tasklet(), but it didn't help either. So far only patch
originally posted here make the problem gone.
Stanislaw
next prev parent reply other threads:[~2019-07-30 13:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-26 12:10 [RFC] mt76: fix tx hung regression on MT7630E Stanislaw Gruszka
2019-07-29 12:53 ` Stanislaw Gruszka
2019-07-29 14:02 ` Lorenzo Bianconi
2019-07-30 13:54 ` Stanislaw Gruszka [this message]
2019-07-30 14:55 ` Lorenzo Bianconi
2019-07-31 8:19 ` Stanislaw Gruszka
2019-07-31 8:51 ` Stanislaw Gruszka
2019-07-31 9:09 ` Lorenzo Bianconi
2019-08-05 10:01 ` Stanislaw Gruszka
2019-08-05 11:27 ` Lorenzo Bianconi
2019-08-05 12:39 ` Stanislaw Gruszka
2019-08-12 11:50 ` Stanislaw Gruszka
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190730135450.GA2361@redhat.com \
--to=sgruszka@redhat.com \
--cc=linux-wireless@vger.kernel.org \
--cc=lorenzo.bianconi@redhat.com \
--cc=nbd@nbd.name \
--cc=royluo@google.com \
--cc=ryder.lee@mediatek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).