linux-kernel - Re: [BUG, bisected] atmel_spi: hard lockups in transfer

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Message-ID: <20080406181817.5824f962@siona.local>
Date:	Sun, 6 Apr 2008 18:18:17 -0400
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	Ben Nizette <bn@...sdigital.com>
Cc:	kernel <kernel@...32linux.org>, slipszi@...il.com,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG, bisected] atmel_spi: hard lockups in transfer

On Sun, 06 Apr 2008 09:28:38 +1000
Ben Nizette <bn@...sdigital.com> wrote:

> Hi,
> 
> For some weeks now there have been reports flying across the main AVR32
> support forum, avrfreaks [1], that atmel_spi now hard-hangs on most
> transfers.  The behaviour is not apparent in .23 and is in .24+.  One
> tester was good enough to bisect the problem and turned up

Thanks for reporting this.

> 154443c72f47169ebcb3a7befbff0e934c49bff3
> atmel_spi: chain DMA transfers
> 
> as the culprit.  The tester also had to revert 
> 
> commit 8bacb219018a52e6f02a3cff6a7badf102ddfc44
> atmel_spi: fix dmachain oops with DEBUG enabled
> 
> when they reverted 154443 as they were not confident enough to resolve
> the conflicts that resulted from just reverting the first one.

That is indeed the correct way to resolve the conflict since the latter
fixes a bug introduced by the former.

> The discussion thread involving this can be seen at [2].
> 
> As I say, this is present in .24+ so any fix will be a stable candidate
> as well as .25 material (if we haven't missed the boat by then).

I'm afraid I don't have much time to look at this right now...but I'll
see what I can do. It's strange that I never noticed this problem
myself -- I did see some overrun issues, but I blamed it on the
throughput improvements and just reduced the speed slightly.

Do you have any special debugging options enabled?

Haavard
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