linux-kernel - Re: [PATCH] Documentation: dmaengine: Add a documentation for the dma controller API

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Message-ID: <20140802151714.GB30282@n2100.arm.linux.org.uk>
Date:	Sat, 2 Aug 2014 16:17:14 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	dmaengine@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Antoine Ténart <antoine@...e-electrons.com>,
	Thomas Petazzoni <thomas@...e-electrons.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Boris Brezillon <boris@...e-electrons.com>,
	Matt Porter <matt.porter@...aro.org>,
	laurent.pinchart@...asonboard.com, ludovic.desroches@...el.com,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH] Documentation: dmaengine: Add a documentation for the
	dma controller API

On Sat, Aug 02, 2014 at 04:49:25PM +0200, Maxime Ripard wrote:
> In the case of the call to device_control, especially in the
> DMA_SLAVE_CONFIG case, but that also applies to pause/resume, are the
> changes supposed to be immediates or can they happen later?

pause/resume are expected to operate synchronously on the channel.
When asking for the channel to pause, the channel must be stopped
before the call returns.

In the case of channel configuration, that should have no effect on
any previously queued transfer - in other words, changing the channel
configuration only has an effect when subsequent transactions are
prepared.

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