diff mbox

[PATCHv9,6/6] dmaengine: rcar-dmac: add iommu support for slave transfers

Message ID 20160810112219.17964-7-niklas.soderlund+renesas@ragnatech.se (mailing list archive)
State New, archived
Headers show

Commit Message

Niklas Söderlund Aug. 10, 2016, 11:22 a.m. UTC
Enable slave transfers to a device behind a IPMMU by mapping the slave
addresses using the dma-mapping API.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
---
 drivers/dma/sh/rcar-dmac.c | 82 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 74 insertions(+), 8 deletions(-)

Comments

Laurent Pinchart Sept. 5, 2016, 9:52 a.m. UTC | #1
Hi Niklas,

Thank you for the patch.

On Wednesday 10 Aug 2016 13:22:19 Niklas Söderlund wrote:
> Enable slave transfers to a device behind a IPMMU by mapping the slave
> addresses using the dma-mapping API.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
> drivers/dma/sh/rcar-dmac.c | 82 ++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 74 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index cf983a9..22a5e40 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -128,6 +128,18 @@ struct rcar_dmac_chan_slave {
>  };
> 
>  /*
> + * struct rcar_dmac_chan_map - Map of slave device phys to dma address
> + * @addr: slave dma address
> + * @dir: direction of mapping
> + * @slave: slave configuration that is mapped
> + */
> +struct rcar_dmac_chan_map {
> +	dma_addr_t addr;
> +	enum dma_data_direction dir;
> +	struct rcar_dmac_chan_slave slave;
> +};
> +
> +/*
>   * struct rcar_dmac_chan - R-Car Gen2 DMA Controller Channel
>   * @chan: base DMA channel object
>   * @iomem: channel I/O memory base
> @@ -152,6 +164,7 @@ struct rcar_dmac_chan {
> 
>  	struct rcar_dmac_chan_slave src;
>  	struct rcar_dmac_chan_slave dst;
> +	struct rcar_dmac_chan_map map;
>  	int mid_rid;
> 
>  	spinlock_t lock;
> @@ -1029,13 +1042,65 @@ rcar_dmac_prep_dma_memcpy(struct dma_chan *chan,
> dma_addr_t dma_dest, DMA_MEM_TO_MEM, flags, false);
>  }
> 
> +static int rcar_dmac_map_slave_addr(struct dma_chan *chan,
> +				    enum dma_transfer_direction dir)
> +{
> +	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
> +	struct rcar_dmac_chan_map *map = &rchan->map;
> +	phys_addr_t dev_addr;
> +	size_t dev_size;
> +	enum dma_data_direction dev_dir;
> +
> +	if (dir == DMA_DEV_TO_MEM) {
> +		dev_addr = rchan->src.slave_addr;
> +		dev_size = rchan->src.xfer_size;
> +		dev_dir = DMA_TO_DEVICE;

Shouldn't this be DMA_FROM_DEVICE, and DMA_TO_DEVICE below ?

> +	} else {
> +		dev_addr = rchan->dst.slave_addr;
> +		dev_size = rchan->dst.xfer_size;
> +		dev_dir = DMA_FROM_DEVICE;
> +	}
> +
> +	/* Reuse current map if possible. */
> +	if (dev_addr == map->slave.slave_addr &&
> +	    dev_size == map->slave.xfer_size &&
> +	    dev_dir == map->dir)
> +		return 0;
> +
> +	/* Remove old mapping if present. */
> +	if (map->slave.xfer_size)
> +		dma_unmap_resource(chan->device->dev, map->addr,
> +				   map->slave.xfer_size, map->dir, 0);

Unless I'm mistaken the resource will not be unmapped when freeing channel 
resources, will it ?

> +	map->slave.xfer_size = 0;
> +
> +	/* Create new slave address map. */
> +	map->addr = dma_map_resource(chan->device->dev, dev_addr, dev_size,
> +				     dev_dir, 0);
> +
> +	if (dma_mapping_error(chan->device->dev, map->addr)) {
> +		dev_err(chan->device->dev,
> +			"chan%u: failed to map %zx@%pap", rchan->index,
> +			dev_size, &dev_addr);
> +		return -EIO;
> +	}
> +
> +	dev_dbg(chan->device->dev, "chan%u: map %zx@%pap to %pad dir: %s\n",
> +		rchan->index, dev_size, &dev_addr, &map->addr,
> +		dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" : 
"DMA_FROM_DEVICE");
> +
> +	map->slave.slave_addr = dev_addr;
> +	map->slave.xfer_size = dev_size;
> +	map->dir = dev_dir;
> +
> +	return 0;
> +}
> +
>  static struct dma_async_tx_descriptor *
>  rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>  			unsigned int sg_len, enum dma_transfer_direction dir,
>  			unsigned long flags, void *context)
>  {
>  	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
> -	dma_addr_t dev_addr;
> 
>  	/* Someone calling slave DMA on a generic channel? */
>  	if (rchan->mid_rid < 0 || !sg_len) {
> @@ -1045,9 +1110,10 @@ rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct
> scatterlist *sgl, return NULL;
>  	}
> 
> -	dev_addr = dir == DMA_DEV_TO_MEM
> -		 ? rchan->src.slave_addr : rchan->dst.slave_addr;
> -	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
> +	if (rcar_dmac_map_slave_addr(chan, dir))
> +		return NULL;
> +
> +	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, rchan->map.addr,
>  				      dir, flags, false);
>  }
> 
> @@ -1061,7 +1127,6 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan,
> dma_addr_t buf_addr, struct rcar_dmac_chan *rchan =
> to_rcar_dmac_chan(chan);
>  	struct dma_async_tx_descriptor *desc;
>  	struct scatterlist *sgl;
> -	dma_addr_t dev_addr;
>  	unsigned int sg_len;
>  	unsigned int i;
> 
> @@ -1073,6 +1138,9 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan,
> dma_addr_t buf_addr, return NULL;
>  	}
> 
> +	if (rcar_dmac_map_slave_addr(chan, dir))
> +		return NULL;
> +
>  	sg_len = buf_len / period_len;
>  	if (sg_len > RCAR_DMAC_MAX_SG_LEN) {
>  		dev_err(chan->device->dev,
> @@ -1100,9 +1168,7 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan,
> dma_addr_t buf_addr, sg_dma_len(&sgl[i]) = period_len;
>  	}
> 
> -	dev_addr = dir == DMA_DEV_TO_MEM
> -		 ? rchan->src.slave_addr : rchan->dst.slave_addr;
> -	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
> +	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, rchan->map.addr,
>  				      dir, flags, true);
> 
>  	kfree(sgl);
Robin Murphy Sept. 5, 2016, 10:37 a.m. UTC | #2
Hi Laurent,

On 05/09/16 10:52, Laurent Pinchart wrote:
> Hi Niklas,
> 
> Thank you for the patch.
> 
> On Wednesday 10 Aug 2016 13:22:19 Niklas Söderlund wrote:
>> Enable slave transfers to a device behind a IPMMU by mapping the slave
>> addresses using the dma-mapping API.
>>
>> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
>> ---
>> drivers/dma/sh/rcar-dmac.c | 82 ++++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 74 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
>> index cf983a9..22a5e40 100644
>> --- a/drivers/dma/sh/rcar-dmac.c
>> +++ b/drivers/dma/sh/rcar-dmac.c
>> @@ -128,6 +128,18 @@ struct rcar_dmac_chan_slave {
>>  };
>>
>>  /*
>> + * struct rcar_dmac_chan_map - Map of slave device phys to dma address
>> + * @addr: slave dma address
>> + * @dir: direction of mapping
>> + * @slave: slave configuration that is mapped
>> + */
>> +struct rcar_dmac_chan_map {
>> +	dma_addr_t addr;
>> +	enum dma_data_direction dir;
>> +	struct rcar_dmac_chan_slave slave;
>> +};
>> +
>> +/*
>>   * struct rcar_dmac_chan - R-Car Gen2 DMA Controller Channel
>>   * @chan: base DMA channel object
>>   * @iomem: channel I/O memory base
>> @@ -152,6 +164,7 @@ struct rcar_dmac_chan {
>>
>>  	struct rcar_dmac_chan_slave src;
>>  	struct rcar_dmac_chan_slave dst;
>> +	struct rcar_dmac_chan_map map;
>>  	int mid_rid;
>>
>>  	spinlock_t lock;
>> @@ -1029,13 +1042,65 @@ rcar_dmac_prep_dma_memcpy(struct dma_chan *chan,
>> dma_addr_t dma_dest, DMA_MEM_TO_MEM, flags, false);
>>  }
>>
>> +static int rcar_dmac_map_slave_addr(struct dma_chan *chan,
>> +				    enum dma_transfer_direction dir)
>> +{
>> +	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
>> +	struct rcar_dmac_chan_map *map = &rchan->map;
>> +	phys_addr_t dev_addr;
>> +	size_t dev_size;
>> +	enum dma_data_direction dev_dir;
>> +
>> +	if (dir == DMA_DEV_TO_MEM) {
>> +		dev_addr = rchan->src.slave_addr;
>> +		dev_size = rchan->src.xfer_size;
>> +		dev_dir = DMA_TO_DEVICE;
> 
> Shouldn't this be DMA_FROM_DEVICE, and DMA_TO_DEVICE below ?

No, this is in fact correct (double-checking against the equivalent I
wrote for the ARM PL330 based on this - I should resurrect those patches...)

The "DEV" in the dmaengine direction is the peripheral FIFO, whereas the
"DEVICE" in the DMA API direction is the DMA engine itself, thus for the
DEV_TO_MEM transaction, the mapping of the "DEV" end needs to allow data
transfer "from" the address being mapped "to" the DMA engine.

Yes, it's hideously confusing.

Robin.

>> +	} else {
>> +		dev_addr = rchan->dst.slave_addr;
>> +		dev_size = rchan->dst.xfer_size;
>> +		dev_dir = DMA_FROM_DEVICE;
>> +	}
>> +
>> +	/* Reuse current map if possible. */
>> +	if (dev_addr == map->slave.slave_addr &&
>> +	    dev_size == map->slave.xfer_size &&
>> +	    dev_dir == map->dir)
>> +		return 0;
>> +
>> +	/* Remove old mapping if present. */
>> +	if (map->slave.xfer_size)
>> +		dma_unmap_resource(chan->device->dev, map->addr,
>> +				   map->slave.xfer_size, map->dir, 0);
> 
> Unless I'm mistaken the resource will not be unmapped when freeing channel 
> resources, will it ?
> 
>> +	map->slave.xfer_size = 0;
>> +
>> +	/* Create new slave address map. */
>> +	map->addr = dma_map_resource(chan->device->dev, dev_addr, dev_size,
>> +				     dev_dir, 0);
>> +
>> +	if (dma_mapping_error(chan->device->dev, map->addr)) {
>> +		dev_err(chan->device->dev,
>> +			"chan%u: failed to map %zx@%pap", rchan->index,
>> +			dev_size, &dev_addr);
>> +		return -EIO;
>> +	}
>> +
>> +	dev_dbg(chan->device->dev, "chan%u: map %zx@%pap to %pad dir: %s\n",
>> +		rchan->index, dev_size, &dev_addr, &map->addr,
>> +		dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" : 
> "DMA_FROM_DEVICE");
>> +
>> +	map->slave.slave_addr = dev_addr;
>> +	map->slave.xfer_size = dev_size;
>> +	map->dir = dev_dir;
>> +
>> +	return 0;
>> +}
>> +
>>  static struct dma_async_tx_descriptor *
>>  rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>>  			unsigned int sg_len, enum dma_transfer_direction dir,
>>  			unsigned long flags, void *context)
>>  {
>>  	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
>> -	dma_addr_t dev_addr;
>>
>>  	/* Someone calling slave DMA on a generic channel? */
>>  	if (rchan->mid_rid < 0 || !sg_len) {
>> @@ -1045,9 +1110,10 @@ rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct
>> scatterlist *sgl, return NULL;
>>  	}
>>
>> -	dev_addr = dir == DMA_DEV_TO_MEM
>> -		 ? rchan->src.slave_addr : rchan->dst.slave_addr;
>> -	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
>> +	if (rcar_dmac_map_slave_addr(chan, dir))
>> +		return NULL;
>> +
>> +	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, rchan->map.addr,
>>  				      dir, flags, false);
>>  }
>>
>> @@ -1061,7 +1127,6 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan,
>> dma_addr_t buf_addr, struct rcar_dmac_chan *rchan =
>> to_rcar_dmac_chan(chan);
>>  	struct dma_async_tx_descriptor *desc;
>>  	struct scatterlist *sgl;
>> -	dma_addr_t dev_addr;
>>  	unsigned int sg_len;
>>  	unsigned int i;
>>
>> @@ -1073,6 +1138,9 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan,
>> dma_addr_t buf_addr, return NULL;
>>  	}
>>
>> +	if (rcar_dmac_map_slave_addr(chan, dir))
>> +		return NULL;
>> +
>>  	sg_len = buf_len / period_len;
>>  	if (sg_len > RCAR_DMAC_MAX_SG_LEN) {
>>  		dev_err(chan->device->dev,
>> @@ -1100,9 +1168,7 @@ rcar_dmac_prep_dma_cyclic(struct dma_chan *chan,
>> dma_addr_t buf_addr, sg_dma_len(&sgl[i]) = period_len;
>>  	}
>>
>> -	dev_addr = dir == DMA_DEV_TO_MEM
>> -		 ? rchan->src.slave_addr : rchan->dst.slave_addr;
>> -	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
>> +	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, rchan->map.addr,
>>  				      dir, flags, true);
>>
>>  	kfree(sgl);
>
Laurent Pinchart Jan. 1, 2017, 11:08 p.m. UTC | #3
Hi Niklas,

On Monday 05 Sep 2016 12:52:44 Laurent Pinchart wrote:
> On Wednesday 10 Aug 2016 13:22:19 Niklas Söderlund wrote:
> > Enable slave transfers to a device behind a IPMMU by mapping the slave
> > addresses using the dma-mapping API.
> > 
> > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > ---
> > drivers/dma/sh/rcar-dmac.c | 82 ++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 74 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> > index cf983a9..22a5e40 100644
> > --- a/drivers/dma/sh/rcar-dmac.c
> > +++ b/drivers/dma/sh/rcar-dmac.c

[snip]

> > +static int rcar_dmac_map_slave_addr(struct dma_chan *chan,
> > +				    enum dma_transfer_direction dir)
> > +{
> > +	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
> > +	struct rcar_dmac_chan_map *map = &rchan->map;
> > +	phys_addr_t dev_addr;
> > +	size_t dev_size;
> > +	enum dma_data_direction dev_dir;
> > +
> > +	if (dir == DMA_DEV_TO_MEM) {
> > +		dev_addr = rchan->src.slave_addr;
> > +		dev_size = rchan->src.xfer_size;
> > +		dev_dir = DMA_TO_DEVICE;
> 
> Shouldn't this be DMA_FROM_DEVICE, and DMA_TO_DEVICE below ?

This comment can be ignored (thank you Robin for the explanation), but ...

> > +	} else {
> > +		dev_addr = rchan->dst.slave_addr;
> > +		dev_size = rchan->dst.xfer_size;
> > +		dev_dir = DMA_FROM_DEVICE;
> > +	}
> > +
> > +	/* Reuse current map if possible. */
> > +	if (dev_addr == map->slave.slave_addr &&
> > +	    dev_size == map->slave.xfer_size &&
> > +	    dev_dir == map->dir)
> > +		return 0;
> > +
> > +	/* Remove old mapping if present. */
> > +	if (map->slave.xfer_size)
> > +		dma_unmap_resource(chan->device->dev, map->addr,
> > +				   map->slave.xfer_size, map->dir, 0);
> 
> Unless I'm mistaken the resource will not be unmapped when freeing channel
> resources, will it ?

I believe this one still needs to be addressed.

> > +	map->slave.xfer_size = 0;
> > +
> > +	/* Create new slave address map. */
> > +	map->addr = dma_map_resource(chan->device->dev, dev_addr, dev_size,
> > +				     dev_dir, 0);
> > +
> > +	if (dma_mapping_error(chan->device->dev, map->addr)) {
> > +		dev_err(chan->device->dev,
> > +			"chan%u: failed to map %zx@%pap", rchan->index,
> > +			dev_size, &dev_addr);
> > +		return -EIO;
> > +	}
> > +
> > +	dev_dbg(chan->device->dev, "chan%u: map %zx@%pap to %pad dir: %s\n",
> > +		rchan->index, dev_size, &dev_addr, &map->addr,
> 
> > +		dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" :
> "DMA_FROM_DEVICE");
> 
> > +
> > +	map->slave.slave_addr = dev_addr;
> > +	map->slave.xfer_size = dev_size;
> > +	map->dir = dev_dir;
> > +
> > +	return 0;
> > +}

[snip]
Niklas Söderlund Jan. 9, 2017, 3:42 p.m. UTC | #4
Hi Laurent,

On 2017-01-02 01:08:04 +0200, Laurent Pinchart wrote:
> Hi Niklas,
> 
> On Monday 05 Sep 2016 12:52:44 Laurent Pinchart wrote:
> > On Wednesday 10 Aug 2016 13:22:19 Niklas Söderlund wrote:
> > > Enable slave transfers to a device behind a IPMMU by mapping the slave
> > > addresses using the dma-mapping API.
> > > 
> > > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > > ---
> > > drivers/dma/sh/rcar-dmac.c | 82 ++++++++++++++++++++++++++++++++++++-----
> > > 1 file changed, 74 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> > > index cf983a9..22a5e40 100644
> > > --- a/drivers/dma/sh/rcar-dmac.c
> > > +++ b/drivers/dma/sh/rcar-dmac.c
> 
> [snip]
> 
> > > +static int rcar_dmac_map_slave_addr(struct dma_chan *chan,
> > > +				    enum dma_transfer_direction dir)
> > > +{
> > > +	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
> > > +	struct rcar_dmac_chan_map *map = &rchan->map;
> > > +	phys_addr_t dev_addr;
> > > +	size_t dev_size;
> > > +	enum dma_data_direction dev_dir;
> > > +
> > > +	if (dir == DMA_DEV_TO_MEM) {
> > > +		dev_addr = rchan->src.slave_addr;
> > > +		dev_size = rchan->src.xfer_size;
> > > +		dev_dir = DMA_TO_DEVICE;
> > 
> > Shouldn't this be DMA_FROM_DEVICE, and DMA_TO_DEVICE below ?
> 
> This comment can be ignored (thank you Robin for the explanation), but ...
> 
> > > +	} else {
> > > +		dev_addr = rchan->dst.slave_addr;
> > > +		dev_size = rchan->dst.xfer_size;
> > > +		dev_dir = DMA_FROM_DEVICE;
> > > +	}
> > > +
> > > +	/* Reuse current map if possible. */
> > > +	if (dev_addr == map->slave.slave_addr &&
> > > +	    dev_size == map->slave.xfer_size &&
> > > +	    dev_dir == map->dir)
> > > +		return 0;
> > > +
> > > +	/* Remove old mapping if present. */
> > > +	if (map->slave.xfer_size)
> > > +		dma_unmap_resource(chan->device->dev, map->addr,
> > > +				   map->slave.xfer_size, map->dir, 0);
> > 
> > Unless I'm mistaken the resource will not be unmapped when freeing channel
> > resources, will it ?
> 
> I believe this one still needs to be addressed.

I believe you are correct, I will look in to it and hopefully submit a 
patch to address it. Thanks for brining it up.

> 
> > > +	map->slave.xfer_size = 0;
> > > +
> > > +	/* Create new slave address map. */
> > > +	map->addr = dma_map_resource(chan->device->dev, dev_addr, dev_size,
> > > +				     dev_dir, 0);
> > > +
> > > +	if (dma_mapping_error(chan->device->dev, map->addr)) {
> > > +		dev_err(chan->device->dev,
> > > +			"chan%u: failed to map %zx@%pap", rchan->index,
> > > +			dev_size, &dev_addr);
> > > +		return -EIO;
> > > +	}
> > > +
> > > +	dev_dbg(chan->device->dev, "chan%u: map %zx@%pap to %pad dir: %s\n",
> > > +		rchan->index, dev_size, &dev_addr, &map->addr,
> > 
> > > +		dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" :
> > "DMA_FROM_DEVICE");
> > 
> > > +
> > > +	map->slave.slave_addr = dev_addr;
> > > +	map->slave.xfer_size = dev_size;
> > > +	map->dir = dev_dir;
> > > +
> > > +	return 0;
> > > +}
> 
> [snip]
> 
> -- 
> Regards,
> 
> Laurent Pinchart
>
diff mbox

Patch

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index cf983a9..22a5e40 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -128,6 +128,18 @@  struct rcar_dmac_chan_slave {
 };
 
 /*
+ * struct rcar_dmac_chan_map - Map of slave device phys to dma address
+ * @addr: slave dma address
+ * @dir: direction of mapping
+ * @slave: slave configuration that is mapped
+ */
+struct rcar_dmac_chan_map {
+	dma_addr_t addr;
+	enum dma_data_direction dir;
+	struct rcar_dmac_chan_slave slave;
+};
+
+/*
  * struct rcar_dmac_chan - R-Car Gen2 DMA Controller Channel
  * @chan: base DMA channel object
  * @iomem: channel I/O memory base
@@ -152,6 +164,7 @@  struct rcar_dmac_chan {
 
 	struct rcar_dmac_chan_slave src;
 	struct rcar_dmac_chan_slave dst;
+	struct rcar_dmac_chan_map map;
 	int mid_rid;
 
 	spinlock_t lock;
@@ -1029,13 +1042,65 @@  rcar_dmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dma_dest,
 				      DMA_MEM_TO_MEM, flags, false);
 }
 
+static int rcar_dmac_map_slave_addr(struct dma_chan *chan,
+				    enum dma_transfer_direction dir)
+{
+	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
+	struct rcar_dmac_chan_map *map = &rchan->map;
+	phys_addr_t dev_addr;
+	size_t dev_size;
+	enum dma_data_direction dev_dir;
+
+	if (dir == DMA_DEV_TO_MEM) {
+		dev_addr = rchan->src.slave_addr;
+		dev_size = rchan->src.xfer_size;
+		dev_dir = DMA_TO_DEVICE;
+	} else {
+		dev_addr = rchan->dst.slave_addr;
+		dev_size = rchan->dst.xfer_size;
+		dev_dir = DMA_FROM_DEVICE;
+	}
+
+	/* Reuse current map if possible. */
+	if (dev_addr == map->slave.slave_addr &&
+	    dev_size == map->slave.xfer_size &&
+	    dev_dir == map->dir)
+		return 0;
+
+	/* Remove old mapping if present. */
+	if (map->slave.xfer_size)
+		dma_unmap_resource(chan->device->dev, map->addr,
+				   map->slave.xfer_size, map->dir, 0);
+	map->slave.xfer_size = 0;
+
+	/* Create new slave address map. */
+	map->addr = dma_map_resource(chan->device->dev, dev_addr, dev_size,
+				     dev_dir, 0);
+
+	if (dma_mapping_error(chan->device->dev, map->addr)) {
+		dev_err(chan->device->dev,
+			"chan%u: failed to map %zx@%pap", rchan->index,
+			dev_size, &dev_addr);
+		return -EIO;
+	}
+
+	dev_dbg(chan->device->dev, "chan%u: map %zx@%pap to %pad dir: %s\n",
+		rchan->index, dev_size, &dev_addr, &map->addr,
+		dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" : "DMA_FROM_DEVICE");
+
+	map->slave.slave_addr = dev_addr;
+	map->slave.xfer_size = dev_size;
+	map->dir = dev_dir;
+
+	return 0;
+}
+
 static struct dma_async_tx_descriptor *
 rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			unsigned int sg_len, enum dma_transfer_direction dir,
 			unsigned long flags, void *context)
 {
 	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
-	dma_addr_t dev_addr;
 
 	/* Someone calling slave DMA on a generic channel? */
 	if (rchan->mid_rid < 0 || !sg_len) {
@@ -1045,9 +1110,10 @@  rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		return NULL;
 	}
 
-	dev_addr = dir == DMA_DEV_TO_MEM
-		 ? rchan->src.slave_addr : rchan->dst.slave_addr;
-	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
+	if (rcar_dmac_map_slave_addr(chan, dir))
+		return NULL;
+
+	return rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, rchan->map.addr,
 				      dir, flags, false);
 }
 
@@ -1061,7 +1127,6 @@  rcar_dmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
 	struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
 	struct dma_async_tx_descriptor *desc;
 	struct scatterlist *sgl;
-	dma_addr_t dev_addr;
 	unsigned int sg_len;
 	unsigned int i;
 
@@ -1073,6 +1138,9 @@  rcar_dmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
 		return NULL;
 	}
 
+	if (rcar_dmac_map_slave_addr(chan, dir))
+		return NULL;
+
 	sg_len = buf_len / period_len;
 	if (sg_len > RCAR_DMAC_MAX_SG_LEN) {
 		dev_err(chan->device->dev,
@@ -1100,9 +1168,7 @@  rcar_dmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
 		sg_dma_len(&sgl[i]) = period_len;
 	}
 
-	dev_addr = dir == DMA_DEV_TO_MEM
-		 ? rchan->src.slave_addr : rchan->dst.slave_addr;
-	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, dev_addr,
+	desc = rcar_dmac_chan_prep_sg(rchan, sgl, sg_len, rchan->map.addr,
 				      dir, flags, true);
 
 	kfree(sgl);