diff mbox series

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

Message ID 20210219124012.92897-7-alexandru.ardelean@analog.com (mailing list archive)
State New
Headers show
Series iio: Add output buffer support | expand

Commit Message

Alexandru Ardelean Feb. 19, 2021, 12:40 p.m. UTC
From: Lars-Peter Clausen <lars@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 <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 .../buffer/industrialio-buffer-dmaengine.c    | 24 ++++++++++++-------
 include/uapi/linux/iio/buffer.h               |  1 +
 2 files changed, 17 insertions(+), 8 deletions(-)

Comments

Jonathan Cameron Feb. 21, 2021, 12:09 p.m. UTC | #1
On Fri, 19 Feb 2021 14:40:12 +0200
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> From: Lars-Peter Clausen <lars@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 <lars@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Series in general looks good to me, but this change needs a little more
detail + probably some level of example userspace flow.

I don't really understand how this is used!

Also, it's easy to test output buffers with the kfifo support so we
should be able to move forward quickly with that part (1-3, 4 is probably
fine as well as clearly harmless).

The dma stuff worries me more, at least partly based on the experience
of the original dma buffers which basically sat their unused (in upstream)
for a very long time.   So to move these forward, they need to come
with users...

Thanks,

Jonathan

> ---
>  .../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
Alexandru Ardelean Feb. 23, 2021, 6:34 a.m. UTC | #2
On Sun, Feb 21, 2021 at 2:11 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Fri, 19 Feb 2021 14:40:12 +0200
> Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
>
> > From: Lars-Peter Clausen <lars@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 <lars@metafoo.de>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> Series in general looks good to me, but this change needs a little more
> detail + probably some level of example userspace flow.
>
> I don't really understand how this is used!
>
> Also, it's easy to test output buffers with the kfifo support so we
> should be able to move forward quickly with that part (1-3, 4 is probably
> fine as well as clearly harmless).
>
> The dma stuff worries me more, at least partly based on the experience
> of the original dma buffers which basically sat their unused (in upstream)
> for a very long time.   So to move these forward, they need to come
> with users...

So, this series will need to be re-sent/re-tested by someone else.
I'm on my last week at ADI and I'm on vacation.

Maybe I can manage to setup something to test as well, but it will take a while.



>
> Thanks,
>
> Jonathan
>
> > ---
> >  .../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
>
diff mbox series

Patch

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