Re: [PATCH 09/18] dmaengine: bcm2835: Add function to handle DMA mapping

Frank Li
2024-06-05T18:13:41Z

On Fri, May 24, 2024 at 07:26:53PM +0100, Dave Stevenson wrote:
> The code handling DMA mapping is currently incorrect and
> needs a sequence of fixups.

Can you descript what incorrect here?

> Move the mapping out into a separate function and structure
> to allow for those fixes to be applied more cleanly.
>
> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> ---
> drivers/dma/bcm2835-dma.c | 46 ++++++++++++++++++++++++++++++++-------
> 1 file changed, 38 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index aefaa1f01d7f..ef1d95bae84e 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -65,6 +65,10 @@ struct bcm2835_cb_entry {
> dma_addr_t paddr;
> };
>
> +struct bcm2835_dma_chan_map {
> + dma_addr_t addr;
> +};
> +
> struct bcm2835_chan {
> struct virt_dma_chan vc;
>
> @@ -74,6 +78,7 @@ struct bcm2835_chan {
> int ch;
> struct bcm2835_desc *desc;
> struct dma_pool *cb_pool;
> + struct bcm2835_dma_chan_map map;

I suppose map should in bcm2835_desc. if put in chan, how about client
driver create two desc by bcm2835_dma_prep_slave_sg()?

prep_slave_sg()
submit()
prep_savle_sg()
submit()
issue_pending()

Frank

>
> void __iomem *chan_base;
> int irq_number;
> @@ -268,6 +273,19 @@ static inline bool need_dst_incr(enum dma_transfer_direction direction)
> }
>
> return false;
> +};
> +
> +static int bcm2835_dma_map_slave_addr(struct dma_chan *chan,
> + phys_addr_t dev_addr,
> + size_t dev_size,
> + enum dma_data_direction dev_dir)
> +{
> + struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
> + struct bcm2835_dma_chan_map *map = &c->map;
> +
> + map->addr = dev_addr;
> +
> + return 0;
> }
>
> static void bcm2835_dma_free_cb_chain(struct bcm2835_desc *desc)
> @@ -734,13 +752,19 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
> }
>
> if (direction == DMA_DEV_TO_MEM) {
> - if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> + if (bcm2835_dma_map_slave_addr(chan, c->cfg.src_addr,
> + c->cfg.src_addr_width,
> + DMA_TO_DEVICE))
> return NULL;
> - src = c->cfg.src_addr;
> +
> + src = c->map.addr;
> } else {
> - if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> + if (bcm2835_dma_map_slave_addr(chan, c->cfg.dst_addr,
> + c->cfg.dst_addr_width,
> + DMA_FROM_DEVICE))
> return NULL;
> - dst = c->cfg.dst_addr;
> +
> + dst = c->map.addr;
> }
>
> /* count frames in sg list */
> @@ -795,14 +819,20 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
> __func__, buf_len, period_len);
>
> if (direction == DMA_DEV_TO_MEM) {
> - if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> + if (bcm2835_dma_map_slave_addr(chan, c->cfg.src_addr,
> + c->cfg.src_addr_width,
> + DMA_TO_DEVICE))
> return NULL;
> - src = c->cfg.src_addr;
> +
> + src = c->map.addr;
> dst = buf_addr;
> } else {
> - if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> + if (bcm2835_dma_map_slave_addr(chan, c->cfg.dst_addr,
> + c->cfg.dst_addr_width,
> + DMA_FROM_DEVICE))
> return NULL;
> - dst = c->cfg.dst_addr;
> +
> + dst = c->map.addr;
> src = buf_addr;
> }
>
> --
> 2.34.1
>