linux-kernel - RE: [PATCH 1/2 v2] dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller

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Date:	Fri, 3 Jul 2009 13:59:24 +0100
From:	"Sosnowski, Maciej" <maciej.sosnowski@...el.com>
To:	Nicolas Ferre <nicolas.ferre@...el.com>
CC:	"Williams, Dan J" <dan.j.williams@...el.com>,
	"avictor.za@...il.com" <avictor.za@...il.com>,
	"linux-arm-kernel@...ts.arm.linux.org.uk" 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	"patrice.vilchez@...el.com" <patrice.vilchez@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2 v2] dmaengine: at_hdmac: new driver for the Atmel
 AHB DMA Controller

Nicolas Ferre wrote:
> This AHB DMA Controller (aka HDMA or DMAC on AT91 systems) is availlable on
> at91sam9rl chip. It will be used on other products in the future.
> 
> This first release covers only the memory-to-memory tranfer type. This is the
> only tranfer type supported by this chip.  On other products, it will be used
> also for peripheral DMA transfer (slave API support to come).
> 
> I used dmatest client without problem in different configurations to test it.
> 
> Full documentation for this controller can be found in the SAM9RL datasheet:
> http://www.atmel.com/dyn/products/product_card.asp?part_id=4243
> 
> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
> ---
[...]
> +	/*
> +	 * We use dma_unmap_page() regardless of how the buffers were
> +	 * mapped before they were submitted...
> +	 */
> +	if (!(txd->flags & DMA_COMPL_SKIP_DEST_UNMAP))
> +		dma_unmap_page(chan2parent(&atchan->chan_common), desc->lli.daddr,
> +				desc->len, DMA_FROM_DEVICE);
> +	if (!(txd->flags & DMA_COMPL_SKIP_SRC_UNMAP))
> +		dma_unmap_page(chan2parent(&atchan->chan_common), desc->lli.saddr,
> +				desc->len, DMA_TO_DEVICE);

It is similar issue as the one fixed in 2.6.30 by 'ioatdma: fix "ioatdma frees DMA memory with wrong function"' patch:
commit 4f005dbe5584fe54c9f6d6d4f0acd3fb29be84da.
Note that this patch introduces dma control flags: DMA_COMPL_SRC_UNMAP_SINGLE and DMA_COMPL_DEST_UNMAP_SINGLE,
that could be used by the driver to choose proper unmapping.

Regards,
Maciej--
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