[RFC v2 10/11] vb2: dma-contig: Let drivers decide DMA attrs of MMAP and USERPTR bufs

[Laurent Pinchart]

From: Sakari Ailus <sakari.ailus at linux.intel.com>

The desirable DMA attributes are not generic for all devices using
Videobuf2 contiguous DMA ops. Let the drivers decide.

This change also results in MMAP buffers always having an sg_table
(dma_sgt field).

Also arrange the header files alphabetically.

As a result, also the DMA-BUF exporter must provide ops for synchronising
the cache. This adds begin_cpu_access and end_cpu_access ops to
vb2_dc_dmabuf_ops.

Signed-off-by: Sakari Ailus <sakari.ailus at linux.intel.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 66 ++++++++++++++++++++++----
 1 file changed, 56 insertions(+), 10 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index d503647ea522..a0e88ad93f07 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -11,11 +11,11 @@
  */
 
 #include <linux/dma-buf.h>
+#include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/scatterlist.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
-#include <linux/dma-mapping.h>
 
 #include <media/videobuf2-v4l2.h>
 #include <media/videobuf2-dma-contig.h>
@@ -115,8 +115,11 @@ static void vb2_dc_prepare(void *buf_priv)
 	struct vb2_dc_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (!buf->vec)
+	/*
+	 * DMABUF exporter will flush the cache for us; only USERPTR
+	 * and MMAP buffers with non-coherent memory will be flushed.
+	 */
+	if (!(buf->attrs & DMA_ATTR_NON_CONSISTENT))
 		return;
 
 	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
@@ -128,8 +131,11 @@ static void vb2_dc_finish(void *buf_priv)
 	struct vb2_dc_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (!buf->vec)
+	/*
+	 * DMABUF exporter will flush the cache for us; only USERPTR
+	 * and MMAP buffers with non-coherent memory will be flushed.
+	 */
+	if (!(buf->attrs & DMA_ATTR_NON_CONSISTENT))
 		return;
 
 	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
@@ -172,13 +178,22 @@ static void *vb2_dc_alloc(struct device *dev, unsigned long attrs,
 	if (attrs)
 		buf->attrs = attrs;
 	buf->cookie = dma_alloc_attrs(dev, size, &buf->dma_addr,
-					GFP_KERNEL | gfp_flags, buf->attrs);
+				     GFP_KERNEL | gfp_flags, buf->attrs);
 	if (!buf->cookie) {
-		dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
+		dev_err(dev, "dma_alloc_attrs of size %ld failed\n", size);
 		kfree(buf);
 		return ERR_PTR(-ENOMEM);
 	}
 
+	if (buf->attrs & DMA_ATTR_NON_CONSISTENT) {
+		buf->dma_sgt = vb2_dc_get_base_sgt(buf);
+		if (!buf->dma_sgt) {
+			dma_free_attrs(dev, size, buf->cookie, buf->dma_addr,
+				       buf->attrs);
+			return ERR_PTR(-ENOMEM);
+		}
+	}
+
 	if ((buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
 		buf->vaddr = buf->cookie;
 
@@ -359,6 +374,34 @@ static void *vb2_dc_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
 	return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
 }
 
+static int vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
+					      enum dma_data_direction direction)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (!(buf->attrs & DMA_ATTR_NON_CONSISTENT))
+		return 0;
+
+	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+
+	return 0;
+}
+
+static int vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
+					    enum dma_data_direction direction)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (!(buf->attrs & DMA_ATTR_NON_CONSISTENT))
+		return 0;
+
+	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+
+	return 0;
+}
+
 static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
 {
 	struct vb2_dc_buf *buf = dbuf->priv;
@@ -379,6 +422,8 @@ static struct dma_buf_ops vb2_dc_dmabuf_ops = {
 	.unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
 	.kmap = vb2_dc_dmabuf_ops_kmap,
 	.kmap_atomic = vb2_dc_dmabuf_ops_kmap,
+	.begin_cpu_access = vb2_dc_dmabuf_ops_begin_cpu_access,
+	.end_cpu_access = vb2_dc_dmabuf_ops_end_cpu_access,
 	.vmap = vb2_dc_dmabuf_ops_vmap,
 	.mmap = vb2_dc_dmabuf_ops_mmap,
 	.release = vb2_dc_dmabuf_ops_release,
@@ -424,11 +469,12 @@ static void vb2_dc_put_userptr(void *buf_priv)
 
 	if (sgt) {
 		/*
-		 * No need to sync to CPU, it's already synced to the CPU
-		 * since the finish() memop will have been called before this.
+		 * Don't ask to skip cache sync in case if the user
+		 * did ask to skip cache flush the last time the
+		 * buffer was dequeued.
 		 */
 		dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
-				   buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
+				   buf->dma_dir, 0);
 		pages = frame_vector_pages(buf->vec);
 		/* sgt should exist only if vector contains pages... */
 		BUG_ON(IS_ERR(pages));
-- 
Regards,

Laurent Pinchart