From: "Michael Büsch" <m@bues.ch>
To: "Rafał Miłecki" <zajec5@gmail.com>
Cc: Thommy Jakobsson <thommyj@gmail.com>,
linville@tuxdriver.com, linux-wireless@vger.kernel.org,
b43-dev@lists.infradead.org, piotras@gmail.com,
Larry.Finger@lwfinger.net
Subject: [PATCH] B43: Handle DMA RX descriptor underrun
Date: Sun, 5 May 2013 21:58:00 +0200 [thread overview]
Message-ID: <20130505215800.65ae7aea@milhouse> (raw)
In-Reply-To: <CACna6rz+PsN1GyniJL7JZJmb7T6Fnk_g101M8DeePr29LsAXaA@mail.gmail.com>
On Sun, 5 May 2013 21:50:33 +0200
Rafa? Mi?ecki <zajec5@gmail.com> wrote:
> 2013/5/5 Michael B?sch <m@bues.ch>:
> > On Sun, 5 May 2013 18:31:20 +0200
> > Rafa? Mi?ecki <zajec5@gmail.com> wrote:
> >
> >> Still worth considering is my previous e-mail. Why writing (for
> >> example) 1 to RXSTOPINDEX doesn't stop firmware from using slot 1?
> >
> > What makes you think this register does not work?
>
> Take a look at this:
>
> [ 327.224976] [DBG] old current:5 new current:6
> [ 327.224982] [DBG] reading slot 5
> [ 327.224997] [DBG] writing stop slot 6
>
> In above ring->slot was 5, but IRQ was generated, and we read new
> "current" using get_current_rxslot. It appeared to be 6. So we read
> packet from slot 5 and then called
> ops->set_current_rxslot(ring, 6);
> AFAIU hardware shouldn't use slot 6, right? But take a look at what
> happens next:
>
> [ 327.319582] [DBG] old current:6 new current:7
> [ 327.319590] [DBG] reading slot 6
> [ 327.319619] [DBG] writing stop slot 7
>
> Hardware generated IRQ and we get_current_rxslot returned 7. It means
> we're allowed to read slots up to 7 (excluding). It other words it
> means firmware used slot 6... but 100ms earlier we forbid firmware to
> use slot 6!
I'd rather say that this is a race condition between your testing code
and the firmware.
--
Michael
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next prev parent reply other threads:[~2013-05-05 19:58 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-23 19:45 [PATCH] B43: Handle DMA RX descriptor underrun Thommy Jakobsson
2013-04-23 20:33 ` [PATCH] b43: rename stop-index DMA op Michael Büsch
2013-04-24 7:00 ` [PATCH] B43: Handle DMA RX descriptor underrun Rafał Miłecki
[not found] ` <20130503173537.GK2069@tuxdriver.com>
2013-05-03 19:40 ` Thommy Jakobsson
2013-05-02 13:06 ` Michael Büsch
2013-05-02 15:01 ` Larry Finger
2013-05-05 12:44 ` Rafał Miłecki
2013-05-05 13:56 ` Michael Büsch
2013-05-05 15:34 ` Rafał Miłecki
2013-05-05 19:09 ` Thommy Jakobsson
2013-05-05 15:43 ` Rafał Miłecki
2013-05-05 16:31 ` Rafał Miłecki
2013-05-05 17:24 ` Michael Büsch
2013-05-05 19:50 ` Rafał Miłecki
2013-05-05 19:58 ` Michael Büsch [this message]
2013-05-05 20:06 ` Thommy Jakobsson
2013-05-05 19:59 ` Thommy Jakobsson
2013-05-05 19:22 ` Larry Finger
2013-05-13 18:27 ` Thommy Jakobsson
2013-05-24 16:49 ` John W. Linville
2013-05-25 19:02 ` Thommy Jakobsson
2013-05-25 19:37 ` Hauke Mehrtens
2013-05-25 19:42 ` Michael Büsch
2013-05-25 20:37 ` Larry Finger
2013-05-28 17:37 ` John W. Linville
2013-06-10 9:40 ` Rafał Miłecki
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