linux-kernel - Re: [PATCH v3 6/8] dmaengine: rcar-dmac: add iommu support for slave transfers

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Message-ID: <56BB15BB.30806@arm.com>
Date:	Wed, 10 Feb 2016 10:49:31 +0000
From:	Robin Murphy <robin.murphy@....com>
To:	Niklas Söderlund 
	<niklas.soderlund+renesas@...natech.se>,
	linux-renesas-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, iommu@...ts.linux-foundation.org
Cc:	linux-arch@...r.kernel.org, arnd@...db.de, geert+renesas@...der.be,
	vinod.koul@...el.com, linus.walleij@...aro.org,
	laurent.pinchart@...asonboard.com, dan.j.williams@...el.com
Subject: Re: [PATCH v3 6/8] dmaengine: rcar-dmac: add iommu support for slave
 transfers

On 10/02/16 00:57, Niklas Söderlund wrote:
> Enable slave transfers to devices behind IPMMU:s by mapping the slave
> addresses using the dma-mapping API.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
> ---
>   drivers/dma/sh/rcar-dmac.c | 57 ++++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 52 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 743873c..268407c 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -1106,21 +1106,68 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
>   	return desc;
>   }
>
> +static int rcar_dmac_set_slave_addr(struct dma_chan *chan,
> +				     struct rcar_dmac_chan_slave *slave,
> +				     phys_addr_t addr, size_t size)
> +{
> +	struct dma_attrs attrs;
> +	enum dma_data_direction dir;
> +
> +	init_dma_attrs(&attrs);
> +	dma_set_attr(DMA_ATTR_NO_KERNEL_MAPPING, &attrs);
> +	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

Now that we have a way to deal with MMIO addresses properly, we don't 
need these any more.

Robin.

> +
> +	/*
> +	 * We can't know the direction at this time, see documentation for
> +	 * 'direction' in struct dma_slave_config.
> +	 */
> +	dir = DMA_BIDIRECTIONAL;
> +
> +	if (slave->xfer_size) {
> +		dma_unmap_resource(chan->device->dev, slave->slave_addr,
> +				slave->xfer_size, dir, &attrs);
> +		slave->slave_addr = 0;
> +		slave->xfer_size = 0;
> +	}
> +
> +	if (size) {
> +		slave->slave_addr = dma_map_resource(chan->device->dev, addr,
> +				size, dir, &attrs);
> +
> +		if (dma_mapping_error(chan->device->dev, slave->slave_addr)) {
> +			struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
> +
> +			dev_err(chan->device->dev,
> +					"chan%u: failed to map %zx@...p",
> +					rchan->index, size, &addr);
> +			return -EIO;
> +		}
> +
> +		slave->xfer_size = size;
> +	}
> +
> +	return 0;
> +}
> +
>   static int rcar_dmac_device_config(struct dma_chan *chan,
>   				   struct dma_slave_config *cfg)
>   {
>   	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
> +	int ret;
>
>   	/*
>   	 * We could lock this, but you shouldn't be configuring the
>   	 * channel, while using it...
>   	 */
> -	rchan->src.slave_addr = cfg->src_addr;
> -	rchan->dst.slave_addr = cfg->dst_addr;
> -	rchan->src.xfer_size = cfg->src_addr_width;
> -	rchan->dst.xfer_size = cfg->dst_addr_width;
>
> -	return 0;
> +	ret = rcar_dmac_set_slave_addr(chan, &rchan->src, cfg->src_addr,
> +			cfg->src_addr_width);
> +	if (ret)
> +		return ret;
> +
> +	ret = rcar_dmac_set_slave_addr(chan, &rchan->dst, cfg->dst_addr,
> +			cfg->dst_addr_width);
> +	return ret;
>   }
>
>   static int rcar_dmac_chan_terminate_all(struct dma_chan *chan)
>