iio: buffer-dmaengine: Support specifying buffer direction

Update the devm_iio_dmaengine_buffer_setup() function to support
specifying the buffer direction.

Update the iio_dmaengine_buffer_submit() function to handle input
buffers as well as output buffers.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-4-5ca45b4de294@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/buffer/industrialio-buffer-dmaengine.c

@@ -64,14 +64,25 @@ static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
 	struct dmaengine_buffer *dmaengine_buffer =
 		iio_buffer_to_dmaengine_buffer(&queue->buffer);
 	struct dma_async_tx_descriptor *desc;
+	enum dma_transfer_direction dma_dir;
+	size_t max_size;
 	dma_cookie_t cookie;
 
-	block->bytes_used = min(block->size, dmaengine_buffer->max_size);
-	block->bytes_used = round_down(block->bytes_used,
-			dmaengine_buffer->align);
+	max_size = min(block->size, dmaengine_buffer->max_size);
+	max_size = round_down(max_size, dmaengine_buffer->align);
+
+	if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN) {
+		block->bytes_used = max_size;
+		dma_dir = DMA_DEV_TO_MEM;
+	} else {
+		dma_dir = DMA_MEM_TO_DEV;
+	}
+
+	if (!block->bytes_used || block->bytes_used > max_size)
+		return -EINVAL;
 
 	desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
-		block->phys_addr, block->bytes_used, DMA_DEV_TO_MEM,
+		block->phys_addr, block->bytes_used, dma_dir,
 		DMA_PREP_INTERRUPT);
 	if (!desc)
 		return -ENOMEM;
@@ -229,9 +240,10 @@ void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
 }
 EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_free, IIO_DMAENGINE_BUFFER);
 
-struct iio_buffer *iio_dmaengine_buffer_setup(struct device *dev,
+struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
 						  struct iio_dev *indio_dev,
-					      const char *channel)
+						  const char *channel,
+						  enum iio_buffer_direction dir)
 {
 	struct iio_buffer *buffer;
 	int ret;
@@ -242,6 +254,8 @@ struct iio_buffer *iio_dmaengine_buffer_setup(struct device *dev,
 
 	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
 
+	buffer->direction = dir;
+
 	ret = iio_device_attach_buffer(indio_dev, buffer);
 	if (ret) {
 		iio_dmaengine_buffer_free(buffer);
@@ -250,7 +264,7 @@ struct iio_buffer *iio_dmaengine_buffer_setup(struct device *dev,
 
 	return buffer;
 }
-EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_setup, IIO_DMAENGINE_BUFFER);
+EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_setup_ext, IIO_DMAENGINE_BUFFER);
 
 static void __devm_iio_dmaengine_buffer_free(void *buffer)
 {
@@ -258,30 +272,32 @@ static void __devm_iio_dmaengine_buffer_free(void *buffer)
 }
 
 /**
- * devm_iio_dmaengine_buffer_setup() - Setup a DMA buffer for an IIO device
+ * devm_iio_dmaengine_buffer_setup_ext() - Setup a DMA buffer for an IIO device
  * @dev: Parent device for the buffer
  * @indio_dev: IIO device to which to attach this buffer.
  * @channel: DMA channel name, typically "rx".
+ * @dir: Direction of buffer (in or out)
  *
  * This allocates a new IIO buffer with devm_iio_dmaengine_buffer_alloc()
  * and attaches it to an IIO device with iio_device_attach_buffer().
  * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of the
  * IIO device.
  */
-int devm_iio_dmaengine_buffer_setup(struct device *dev,
+int devm_iio_dmaengine_buffer_setup_ext(struct device *dev,
 					struct iio_dev *indio_dev,
-				    const char *channel)
+					const char *channel,
+					enum iio_buffer_direction dir)
 {
 	struct iio_buffer *buffer;
 
-	buffer = iio_dmaengine_buffer_setup(dev, indio_dev, channel);
+	buffer = iio_dmaengine_buffer_setup_ext(dev, indio_dev, channel, dir);
 	if (IS_ERR(buffer))
 		return PTR_ERR(buffer);
 
 	return devm_add_action_or_reset(dev, __devm_iio_dmaengine_buffer_free,
 					buffer);
 }
-EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup, IIO_DMAENGINE_BUFFER);
+EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_ext, IIO_DMAENGINE_BUFFER);
 
 MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
 MODULE_DESCRIPTION("DMA buffer for the IIO framework");

include/linux/iio/buffer-dmaengine.h

@@ -7,15 +7,28 @@
 #ifndef __IIO_DMAENGINE_H__
 #define __IIO_DMAENGINE_H__
 
+#include <linux/iio/buffer.h>
+
 struct iio_dev;
 struct device;
 
 void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
-struct iio_buffer *iio_dmaengine_buffer_setup(struct device *dev,
+struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
 						  struct iio_dev *indio_dev,
-					      const char *channel);
-int devm_iio_dmaengine_buffer_setup(struct device *dev,
+						  const char *channel,
+						  enum iio_buffer_direction dir);
+
+#define iio_dmaengine_buffer_setup(dev, indio_dev, channel)	\
+	iio_dmaengine_buffer_setup_ext(dev, indio_dev, channel,	\
+				       IIO_BUFFER_DIRECTION_IN)
+
+int devm_iio_dmaengine_buffer_setup_ext(struct device *dev,
 					struct iio_dev *indio_dev,
-				    const char *channel);
+					const char *channel,
+					enum iio_buffer_direction dir);
+
+#define devm_iio_dmaengine_buffer_setup(dev, indio_dev, channel)	\
+	devm_iio_dmaengine_buffer_setup_ext(dev, indio_dev, channel,	\
+					    IIO_BUFFER_DIRECTION_IN)
 
 #endif