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

Laurent Pinchart
2016-12-16T01:24:05Z

From: Sakari Ailus <sakari.ailus@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@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));