On Fri, 12 Feb 2021 12:20:21 +0200
Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> wrote:
> From: Lars-Peter Clausen <lars@xxxxxxxxxx>
>
> This change adds support for cyclic DMA transfers using the IIO buffer DMA
> infrastructure.
> To do this, userspace must set the IIO_BUFFER_BLOCK_FLAG_CYCLIC flag on the
> block when enqueueing them via the ENQUEUE_BLOCK ioctl().
We should have more than that in the way of documentation!
What is the dataflow that we end up with as a result of this?
Jonathan
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
> ---
> .../buffer/industrialio-buffer-dmaengine.c | 24 ++++++++++++-------
> include/uapi/linux/iio/buffer.h | 1 +
> 2 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> index 013cc7c1ecf4..94c93a636ad4 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> @@ -82,14 +82,22 @@ static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
>
> direction = dmaengine_buffer->is_tx ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM;
>
> - desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
> - block->phys_addr, block->block.bytes_used, direction,
> - DMA_PREP_INTERRUPT);
> - if (!desc)
> - return -ENOMEM;
> -
> - desc->callback_result = iio_dmaengine_buffer_block_done;
> - desc->callback_param = block;
> + if (block->block.flags & IIO_BUFFER_BLOCK_FLAG_CYCLIC) {
> + desc = dmaengine_prep_dma_cyclic(dmaengine_buffer->chan,
> + block->phys_addr, block->block.bytes_used,
> + block->block.bytes_used, direction, 0);
> + if (!desc)
> + return -ENOMEM;
> + } else {
> + desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
> + block->phys_addr, block->block.bytes_used, direction,
> + DMA_PREP_INTERRUPT);
> + if (!desc)
> + return -ENOMEM;
> +
> + desc->callback_result = iio_dmaengine_buffer_block_done;
> + desc->callback_param = block;
> + }
>
> cookie = dmaengine_submit(desc);
> if (dma_submit_error(cookie))
> diff --git a/include/uapi/linux/iio/buffer.h b/include/uapi/linux/iio/buffer.h
> index 70ad3aea01ea..0e0c95f1c38b 100644
> --- a/include/uapi/linux/iio/buffer.h
> +++ b/include/uapi/linux/iio/buffer.h
> @@ -13,6 +13,7 @@ struct iio_buffer_block_alloc_req {
> };
>
> #define IIO_BUFFER_BLOCK_FLAG_TIMESTAMP_VALID (1 << 0)
> +#define IIO_BUFFER_BLOCK_FLAG_CYCLIC (1 << 1)
>
> struct iio_buffer_block {
> __u32 id;
