Re: [PATCH 11/18] dmaengine: bcm2835: Use dma_map_resource to map addresses

Frank Li
2024-06-05T18:22:41Z

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
>