linux-kernel - Re: [PATCH 1/2] dmaengine: bcm2835: Fix cyclic DMA period splitting

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Message-ID: <87a8iowf1l.fsf@eliezer.anholt.net>
Date:	Mon, 13 Jun 2016 21:49:26 -0700
From:	Eric Anholt <eric@...olt.net>
To:	Matthias Reichl <hias@...us.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee@...nel.org>
Cc:	Martin Sperl <kernel@...tin.sperl.org>,
	Clive Messer <clive.messer@...italdreamtime.co.uk>,
	dmaengine@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dmaengine: bcm2835: Fix cyclic DMA period splitting

Matthias Reichl <hias@...us.com> writes:

> The code responsible for splitting periods into chunks that
> can be handled by the DMA controller missed to update total_len,
> the number of bytes processed in the current period, when there
> are more chunks to follow.
>
> Therefore total_len was stuck at 0 and the code didn't work at all.
> This resulted in a wrong control block layout and audio issues because
> the cyclic DMA callback wasn't executing on period boundaries.
>
> Fix this by adding the missing total_len update.

It looks like this issue has been around for a long time, and this fix
is pretty dependent on the recent refactors.

Reviewed-by: Eric Anholt <eric@...olt.net>

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