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

Dave Stevenson
2024-05-24T18:27:59Z

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.

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;
}

- /*
- * 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