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Subject[PATCHv4 02/11] videobuf2: handle V4L2 buffer cache flags
Date
Set video buffer cache management flags corresponding to V4L2 cache
flags.

Both ->prepare() and ->finish() cache management hints should be
passed during this stage (buffer preparation), because there is
no other way for user-space to tell V4L2 to avoid ->finish() cache
flush.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
.../media/common/videobuf2/videobuf2-v4l2.c | 49 +++++++++++++++++++
include/media/videobuf2-core.h | 11 +++++
2 files changed, 60 insertions(+)

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index eb5d5db96552..2a604bd7793a 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -199,6 +199,15 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
vbuf->request_fd = -1;
vbuf->is_held = false;

+ /*
+ * Clear buffer cache flags if queue does not support user space hints.
+ * That's to indicate to userspace that these flags won't work.
+ */
+ if (!vb2_queue_allows_cache_hints(q)) {
+ b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_INVALIDATE;
+ b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_CLEAN;
+ }
+
if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
switch (b->memory) {
case VB2_MEMORY_USERPTR:
@@ -337,6 +346,45 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
return 0;
}

+static void set_buffer_cache_hints(struct vb2_queue *q,
+ struct vb2_buffer *vb,
+ struct v4l2_buffer *b)
+{
+ /*
+ * DMA exporter should take care of cache syncs, so we can avoid
+ * explicit ->prepare()/->finish() syncs. For other ->memory types
+ * we always need ->prepare() or/and ->finish() cache sync.
+ */
+ if (q->memory == VB2_MEMORY_DMABUF) {
+ vb->need_cache_sync_on_finish = 0;
+ vb->need_cache_sync_on_prepare = 0;
+ return;
+ }
+
+ /*
+ * Cache sync/invalidation flags are set by default in order to
+ * preserve existing behaviour for old apps/drivers.
+ */
+ vb->need_cache_sync_on_prepare = 1;
+ vb->need_cache_sync_on_finish = 1;
+
+ if (!vb2_queue_allows_cache_hints(q))
+ return;
+
+ /*
+ * ->finish() cache sync can be avoided when queue direction is
+ * TO_DEVICE.
+ */
+ if (q->dma_dir == DMA_TO_DEVICE)
+ vb->need_cache_sync_on_finish = 0;
+
+ if (b->flags & V4L2_BUF_FLAG_NO_CACHE_INVALIDATE)
+ vb->need_cache_sync_on_finish = 0;
+
+ if (b->flags & V4L2_BUF_FLAG_NO_CACHE_CLEAN)
+ vb->need_cache_sync_on_prepare = 0;
+}
+
static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
struct v4l2_buffer *b, bool is_prepare,
struct media_request **p_req)
@@ -381,6 +429,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
}

if (!vb->prepared) {
+ set_buffer_cache_hints(q, vb, b);
/* Copy relevant information provided by the userspace */
memset(vbuf->planes, 0,
sizeof(vbuf->planes[0]) * vb->num_planes);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 4a19170672ac..731fd9fbd506 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -632,6 +632,17 @@ struct vb2_queue {
#endif
};

+/**
+ * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
+ * and memory consistency hints.
+ *
+ * @q: pointer to &struct vb2_queue with videobuf2 queue
+ */
+static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
+{
+ return q->allow_cache_hints && q->memory == VB2_MEMORY_MMAP;
+}
+
/**
* vb2_plane_vaddr() - Return a kernel virtual address of a given plane.
* @vb: pointer to &struct vb2_buffer to which the plane in
--
2.25.0.265.gbab2e86ba0-goog
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