[PATCH v3 6/6] iio: buffer-dma: add support for cyclic DMA transfers

[Alexandru Ardelean]

From: Lars-Peter Clausen <l...@metafoo.de>

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().

Signed-off-by: Lars-Peter Clausen <l...@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardel...@analog.com>
---
 .../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 65458a6cc81a..39cc230c7991 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 4e4ee9befea1..1bde508fe1b9 100644
--- a/include/uapi/linux/iio/buffer.h
+++ b/include/uapi/linux/iio/buffer.h
@@ -33,6 +33,7 @@ struct iio_buffer_block_alloc_req {
 
 /* A function will be assigned later for BIT(0) */
 #define IIO_BUFFER_BLOCK_FLAG_RESERVED         (1 << 0)
+#define IIO_BUFFER_BLOCK_FLAG_CYCLIC           (1 << 1)
 
 /**
  * struct iio_buffer_block - Descriptor for a single IIO block
-- 
2.27.0