linux-kernel - RE: [PATCH 05/18] ioat2+: add fence support

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Date:	Tue, 15 Sep 2009 17:06:52 +0100
From:	"Sosnowski, Maciej" <maciej.sosnowski@...el.com>
To:	"Williams, Dan J" <dan.j.williams@...el.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>
Subject: RE: [PATCH 05/18] ioat2+: add fence support

Williams, Dan J wrote:
> In preparation for adding more operation types to the ioat3 path the
> driver needs to honor the DMA_PREP_FENCE flag.  For example the async_tx api
> will hand xor->memcpy->xor chains to the driver with the 'fence' flag set on
> the first xor and the memcpy operation.  This flag in turn sets the 'fence'
> flag in the descriptor control field telling the hardware that future
> descriptors in the chain depend on the result of the current descriptor, so
> wait for all writes to complete before starting the next operation.
> 
> Note that ioat1 does not prefetch the descriptor chain, so does not
> require/support fenced operations.
> 
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@...el.com>--
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