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Date: Thu, 14 Mar 2013 21:17:18 +0100
Message-ID: <CACna6rzvqo-CdrwkSH0p9=b=Qn+L78jQQSuGcGbgT865_uKvSw@mail.gmail.com> (sfid-20130314_211729_637144_644B46F6)
Subject: Re: [RFC/RFT] b43: A fix for DMA transmission sequence errors
From: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <zajec5@gmail.com>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Michael Buesch <mb@bu3sch.de>, isedev@gmail.com,
	b43-dev@lists.infradead.org, linux-wireless@vger.kernel.org
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Sender: linux-wireless-owner@vger.kernel.org

2013/3/14 Larry Finger <Larry.Finger@lwfinger.net>:
> From: Iestyn C. Elfick <isedev@gmail.com>
>
> Intermittently, b43 will report "Out of order TX status report on DMA ring".
> When this happens, the driver must be reset before communication can resume.
> The cause of the problem is believed to be an error in the closed-source
> firmware; however, all versions of the firmware are affected.
>
> This change uses the observation that the expected status is always 2 less
> than the observed value, and supplies a fake status report to skip one
> header/data pair.
>
> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
> Cc: Stable <stable@vger.kernel.org>
> ---
>
> Although this is a hack, it seems to work for the OP. It should not cause any
> ill effects on any device that does not have the problem.
>
> It does need a lot more testing, particularly on systems prone to the out-of-order
> status report problem.
>
> If anyone can think of a cleaner, less intrusive solution, please let us know.

I wonder if this is hardware supporting unaligned access with
full-addressing for DMA engine. Maybe it support index-based indexes
for backward compatibility only, and it's somehow broken?

Can we test full-addressing first? I'll try to prepare a patch for
this during the weekend.

-- 
Rafał