Re: [PATCH v5] [media] vb2: Add support for capture_dma_bidirectional queue flag

Thierry Escande <thierry.escande@xxxxxxxxxxxxx> · Tue, 22 Nov 2016 14:30:47 +0100

Hi Mauro,

On 18/11/2016 19:59, Mauro Carvalho Chehab wrote:
Em Tue, 25 Oct 2016 10:22:29 +0200
Thierry Escande <thierry.escande@xxxxxxxxxxxxx> escreveu:

From: Pawel Osciak <posciak@xxxxxxxxxxxx>

When this flag is set for CAPTURE queues by the driver on calling
vb2_queue_init(), it forces the buffers on the queue to be
allocated/mapped with DMA_BIDIRECTIONAL direction flag instead of
DMA_FROM_DEVICE. This allows the device not only to write to the
buffers, but also read out from them. This may be useful e.g. for codec
hardware which may be using CAPTURE buffers as reference to decode
other buffers.

This flag is ignored for OUTPUT queues as we don't want to allow HW to
be able to write to OUTPUT buffers.

This patch introduces 2 macros:
VB2_DMA_DIR(q) returns the corresponding dma_dir for the passed queue
type, tanking care of the capture_dma_birectional flag.

VB2_DMA_DIR_CAPTURE(d) is a test macro returning true if the passed DMA
direction refers to a capture buffer. This test is used to map virtual
addresses for writing and to mark pages as dirty.

Why to add it? There's no other patch on this series with would
justify its needs...

It is used by a Rockchip vpu driver which is only in the chromeos public 
tree for now and will be upstreamed soon.

Regards,
 Thierry


Signed-off-by: Pawel Osciak <posciak@xxxxxxxxxxxx>
Tested-by: Pawel Osciak <posciak@xxxxxxxxxxxx>
Signed-off-by: Thierry Escande <thierry.escande@xxxxxxxxxxxxx>
---

Changes in v2:
- Renamed use_dma_bidirectional field as capture_dma_bidirectional
- Added a VB2_DMA_DIR() macro

Changes in v3:
- Get rid of dma_dir field and therefore squashed the previous patch

Changes in v4:
- Fixed typos in include/media/videobuf2-core.h
- Added VB2_DMA_DIR_CAPTURE() test macro

Changes in v5:
- Use is_output queue field in VB2_DMA_DIR() macro

 drivers/media/v4l2-core/videobuf2-core.c       |  9 +++------
 drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
 drivers/media/v4l2-core/videobuf2-dma-sg.c     |  5 +++--
 drivers/media/v4l2-core/videobuf2-vmalloc.c    |  4 ++--
 include/media/videobuf2-core.h                 | 23 +++++++++++++++++++++++
 5 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 21900202..22d6105 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -194,8 +194,7 @@ static void __enqueue_in_driver(struct vb2_buffer *vb);
 static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
 {
 	struct vb2_queue *q = vb->vb2_queue;
-	enum dma_data_direction dma_dir =
-		q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	enum dma_data_direction dma_dir = VB2_DMA_DIR(q);
 	void *mem_priv;
 	int plane;
 	int ret = -ENOMEM;
@@ -978,8 +977,7 @@ static int __qbuf_userptr(struct vb2_buffer *vb, const void *pb)
 	void *mem_priv;
 	unsigned int plane;
 	int ret = 0;
-	enum dma_data_direction dma_dir =
-		q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	enum dma_data_direction dma_dir = VB2_DMA_DIR(q);
 	bool reacquired = vb->planes[0].mem_priv == NULL;

 	memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
@@ -1096,8 +1094,7 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb, const void *pb)
 	void *mem_priv;
 	unsigned int plane;
 	int ret = 0;
-	enum dma_data_direction dma_dir =
-		q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	enum dma_data_direction dma_dir = VB2_DMA_DIR(q);
 	bool reacquired = vb->planes[0].mem_priv == NULL;

 	memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index fb6a177..a44e383 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -507,7 +507,7 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 	buf->dma_dir = dma_dir;

 	offset = vaddr & ~PAGE_MASK;
-	vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE);
+	vec = vb2_create_framevec(vaddr, size, VB2_DMA_DIR_CAPTURE(dma_dir));
 	if (IS_ERR(vec)) {
 		ret = PTR_ERR(vec);
 		goto fail_buf;
diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index ecff8f49..51c98f6 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -238,7 +238,8 @@ static void *vb2_dma_sg_get_userptr(struct device *dev, unsigned long vaddr,
 	buf->offset = vaddr & ~PAGE_MASK;
 	buf->size = size;
 	buf->dma_sgt = &buf->sg_table;
-	vec = vb2_create_framevec(vaddr, size, buf->dma_dir == DMA_FROM_DEVICE);
+	vec = vb2_create_framevec(vaddr, size,
+				  VB2_DMA_DIR_CAPTURE(buf->dma_dir));
 	if (IS_ERR(vec))
 		goto userptr_fail_pfnvec;
 	buf->vec = vec;
@@ -291,7 +292,7 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
 		vm_unmap_ram(buf->vaddr, buf->num_pages);
 	sg_free_table(buf->dma_sgt);
 	while (--i >= 0) {
-		if (buf->dma_dir == DMA_FROM_DEVICE)
+		if (VB2_DMA_DIR_CAPTURE(buf->dma_dir))
 			set_page_dirty_lock(buf->pages[i]);
 	}
 	vb2_destroy_framevec(buf->vec);
diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
index ab3227b..76649bd 100644
--- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
+++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
@@ -86,7 +86,7 @@ static void *vb2_vmalloc_get_userptr(struct device *dev, unsigned long vaddr,
 	buf->dma_dir = dma_dir;
 	offset = vaddr & ~PAGE_MASK;
 	buf->size = size;
-	vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE);
+	vec = vb2_create_framevec(vaddr, size, VB2_DMA_DIR_CAPTURE(dma_dir));
 	if (IS_ERR(vec)) {
 		ret = PTR_ERR(vec);
 		goto fail_pfnvec_create;
@@ -136,7 +136,7 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
 		pages = frame_vector_pages(buf->vec);
 		if (vaddr)
 			vm_unmap_ram((void *)vaddr, n_pages);
-		if (buf->dma_dir == DMA_FROM_DEVICE)
+		if (VB2_DMA_DIR_CAPTURE(buf->dma_dir))
 			for (i = 0; i < n_pages; i++)
 				set_page_dirty_lock(pages[i]);
 	} else {
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index ac5898a..11d2e51 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -433,6 +433,9 @@ struct vb2_buf_ops {
  * @quirk_poll_must_check_waiting_for_buffers: Return POLLERR at poll when QBUF
  *              has not been called. This is a vb1 idiom that has been adopted
  *              also by vb2.
+ * @capture_dma_bidirectional:	use DMA_BIDIRECTIONAL for CAPTURE buffers; this
+ *				allows HW to read from the CAPTURE buffers in
+ *				addition to writing; ignored for OUTPUT queues.
  * @lock:	pointer to a mutex that protects the vb2_queue struct. The
  *		driver can set this to a mutex to let the v4l2 core serialize
  *		the queuing ioctls. If the driver wants to handle locking
@@ -499,6 +502,7 @@ struct vb2_queue {
 	unsigned			fileio_write_immediately:1;
 	unsigned			allow_zero_bytesused:1;
 	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
+	unsigned			capture_dma_bidirectional:1;

 	struct mutex			*lock;
 	void				*owner;
@@ -554,6 +558,25 @@ struct vb2_queue {
 #endif
 };

+/*
+ * Returns the corresponding DMA direction given the vb2_queue type (capture or
+ * output). Returns DMA_BIDIRECTIONAL for capture buffers if the vb2_queue field
+ * capture_dma_bidirectional is set by the driver.
+ */
+#define VB2_DMA_DIR(q) ((q)->is_output ? DMA_TO_DEVICE                  \
+				       : (q)->capture_dma_bidirectional \
+					 ? DMA_BIDIRECTIONAL            \
+					 : DMA_FROM_DEVICE)
+
+/*
+ * Returns true if the DMA direction passed as parameter refers to a capture
+ * buffer as capture buffers allow both FROM_DEVICE and BIDIRECTIONAL DMA
+ * direction. This test is used to map virtual addresses for writing and to mark
+ * pages as dirty.
+ */
+#define VB2_DMA_DIR_CAPTURE(d) \
+			((d) == DMA_FROM_DEVICE || (d) == DMA_BIDIRECTIONAL)
+
 /**
  * vb2_plane_vaddr() - Return a kernel virtual address of a given plane
  * @vb:		vb2_buffer to which the plane in question belongs to


Thanks,
Mauro

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