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Date: Wed, 5 Jun 2024 14:22:26 -0400
From: Frank Li <Frank.li@nxp.com>
To: Dave Stevenson <dave.stevenson@raspberrypi.com>
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Subject: Re: [PATCH 11/18] dmaengine: bcm2835: Use dma_map_resource to map
 addresses
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References: <20240524182702.1317935-1-dave.stevenson@raspberrypi.com>
 <20240524182702.1317935-12-dave.stevenson@raspberrypi.com>
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On Fri, May 24, 2024 at 07:26:55PM +0100, Dave Stevenson wrote:
> There is a need to account for dma-ranges and iommus in the
> dma mapping process, and the public API for handling that is
> dma_map_resource.

what's means?

> 
> Add support for mapping addresses to the DMA driver.
> 
> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> ---
>  drivers/dma/bcm2835-dma.c | 46 ++++++++++++++++++++++++++++++++++-----
>  1 file changed, 41 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index 9531c0b82071..e48008b06716 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -67,6 +67,10 @@ struct bcm2835_cb_entry {
>  
>  struct bcm2835_dma_chan_map {
>  	dma_addr_t addr;
> +	enum dma_data_direction dir;
> +
> +	phys_addr_t slave_addr;
> +	unsigned int xfer_size;
>  };
>  
>  struct bcm2835_chan {
> @@ -294,12 +298,44 @@ static int bcm2835_dma_map_slave_addr(struct dma_chan *chan,
>  		return 0;
>  	}

where umap function? I suppose you should unmap all when terminate chan
or free chan by client driver. 

>  
> -	/*
> -	 * This path will be updated to handle new clients, but currently should
> -	 * never be used.
> -	 */
> +	if (dev_size != DMA_SLAVE_BUSWIDTH_4_BYTES)
> +		return -EIO;
> +
> +	/* Reuse current map if possible. */
> +	if (dev_addr == map->slave_addr &&
> +	    dev_size == map->xfer_size &&
> +	    dev_dir == map->dir)
> +		return 0;
> +
> +	/* Remove old mapping if present. */
> +	if (map->xfer_size) {
> +		dev_dbg(chan->device->dev, "chan: unmap %zx@%pap to %pad dir: %s\n",
> +			dev_size, &dev_addr, &map->addr,
> +			dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" : "DMA_FROM_DEVICE");
> +		dma_unmap_resource(chan->device->dev, map->addr,
> +				   map->xfer_size, map->dir, 0);
> +	}
> +	map->xfer_size = 0;
>  
> -	return -EINVAL;
> +	/* 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: failed to map %zx@%pap",
> +			dev_size, &dev_addr);
> +		return -EIO;
> +	}
> +
> +	dev_dbg(chan->device->dev, "chan: map %zx@%pap to %pad dir: %s\n",
> +		dev_size, &dev_addr, &map->addr,
> +		dev_dir == DMA_TO_DEVICE ? "DMA_TO_DEVICE" : "DMA_FROM_DEVICE");
> +
> +	map->slave_addr = dev_addr;
> +	map->xfer_size = dev_size;
> +	map->dir = dev_dir;
> +
> +	return 0;
>  }
>  
>  static void bcm2835_dma_free_cb_chain(struct bcm2835_desc *desc)
> -- 
> 2.34.1
>