media: vb2: add bidirectional flag in vb2_queue

This change is intended to give to the v4l2 drivers a choice to
change the default behavior of the v4l2-core DMA mapping direction
from DMA_TO/FROM_DEVICE (depending on the buffer type CAPTURE or
OUTPUT) to DMA_BIDIRECTIONAL during queue_init time.

Initially the issue with DMA mapping direction has been found in
Venus encoder driver where the hardware (firmware side) adds few
lines padding on bottom of the image buffer, and the consequence
is triggering of IOMMU protection faults.

This will help supporting venus encoder (and probably other drivers
in the future) which wants to map output type of buffers as
read/write.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index cb97c22..ef9b643 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -427,6 +427,16 @@ struct vb2_buf_ops {
  * @dev:	device to use for the default allocation context if the driver
  *		doesn't fill in the @alloc_devs array.
  * @dma_attrs:	DMA attributes to use for the DMA.
+ * @bidirectional: when this flag is set the DMA direction for the buffers of
+ *		this queue will be overridden with DMA_BIDIRECTIONAL direction.
+ *		This is useful in cases where the hardware (firmware) writes to
+ *		a buffer which is mapped as read (DMA_TO_DEVICE), or reads from
+ *		buffer which is mapped for write (DMA_FROM_DEVICE) in order
+ *		to satisfy some internal hardware restrictions or adds a padding
+ *		needed by the processing algorithm. In case the DMA mapping is
+ *		not bidirectional but the hardware (firmware) trying to access
+ *		the buffer (in the opposite direction) this could lead to an
+ *		IOMMU protection faults.
  * @fileio_read_once:		report EOF after reading the first buffer
  * @fileio_write_immediately:	queue buffer after each write() call
  * @allow_zero_bytesused:	allow bytesused == 0 to be passed to the driver
@@ -465,6 +475,7 @@ struct vb2_buf_ops {
  * Private elements (won't appear at the uAPI book):
  * @mmap_lock:	private mutex used when buffers are allocated/freed/mmapped
  * @memory:	current memory type used
+ * @dma_dir:	DMA mapping direction.
  * @bufs:	videobuf buffer structures
  * @num_buffers: number of allocated/used buffers
  * @queued_list: list of buffers currently queued from userspace
@@ -495,6 +506,7 @@ struct vb2_queue {
 	unsigned int			io_modes;
 	struct device			*dev;
 	unsigned long			dma_attrs;
+	unsigned			bidirectional:1;
 	unsigned			fileio_read_once:1;
 	unsigned			fileio_write_immediately:1;
 	unsigned			allow_zero_bytesused:1;
@@ -516,6 +528,7 @@ struct vb2_queue {
 	/* private: internal use only */
 	struct mutex			mmap_lock;
 	unsigned int			memory;
+	enum dma_data_direction		dma_dir;
 	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
 	unsigned int			num_buffers;