[media] vb2: use dma_map_sg_attrs to prevent unnecessary sync

By default dma_map_sg syncs the mapped buffer to the device. But
buf_prepare expects a buffer syncs for the cpu and the buffer
will be synced to the device in the prepare memop.

The reverse is true for dma_unmap_sg, buf_finish and the finish
memop.

To prevent unnecessary syncs we ask dma_(un)map_sg to skip the
sync.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

2 files changed, 47 insertions, 10 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 0bfc488c8812..b481d20c8372 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -511,7 +511,15 @@ static void vb2_dc_put_userptr(void *buf_priv)
         struct sg_table *sgt = buf->dma_sgt;
 
         if (sgt) {
-                dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
+                DEFINE_DMA_ATTRS(attrs);
+
+                dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
+                /*
+                 * No need to sync to CPU, it's already synced to the CPU
+                 * since the finish() memop will have been called before this.
+                 */
+                dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
+                                   buf->dma_dir, &attrs);
                 if (!vma_is_io(buf->vma))
                         vb2_dc_sgt_foreach_page(sgt, vb2_dc_put_dirty_page);
 
@@ -568,6 +576,9 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
         struct sg_table *sgt;
         unsigned long contig_size;
         unsigned long dma_align = dma_get_cache_alignment();
+        DEFINE_DMA_ATTRS(attrs);
+
+        dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
 
         /* Only cache aligned DMA transfers are reliable */
         if (!IS_ALIGNED(vaddr | size, dma_align)) {
@@ -654,8 +665,12 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
         kfree(pages);
         pages = NULL;
 
-        sgt->nents = dma_map_sg(buf->dev, sgt->sgl, sgt->orig_nents,
-                buf->dma_dir);
+        /*
+         * No need to sync to the device, this will happen later when the
+         * prepare() memop is called.
+         */
+        sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
+                                      buf->dma_dir, &attrs);
         if (sgt->nents <= 0) {
                 pr_err("failed to map scatterlist\n");
                 ret = -EIO;
@@ -677,7 +692,8 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
         return buf;
 
 fail_map_sg:
-        dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
+        dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
+                           buf->dma_dir, &attrs);
 
 fail_sgt_init:
         if (!vma_is_io(buf->vma))
diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index 0566e94a5a1d..b1838abb6d00 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -107,6 +107,9 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size,
         struct sg_table *sgt;
         int ret;
         int num_pages;
+        DEFINE_DMA_ATTRS(attrs);
+
+        dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
 
         if (WARN_ON(alloc_ctx == NULL))
                 return NULL;
@@ -140,9 +143,13 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size,
         buf->dev = get_device(conf->dev);
 
         sgt = &buf->sg_table;
-        if (dma_map_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir) == 0)
+        /*
+         * No need to sync to the device, this will happen later when the
+         * prepare() memop is called.
+         */
+        if (dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->nents,
+                             buf->dma_dir, &attrs) == 0)
                 goto fail_map;
-        dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
 
         buf->handler.refcount = &buf->refcount;
         buf->handler.put = vb2_dma_sg_put;
@@ -175,9 +182,13 @@ static void vb2_dma_sg_put(void *buf_priv)
         int i = buf->num_pages;
 
         if (atomic_dec_and_test(&buf->refcount)) {
+                DEFINE_DMA_ATTRS(attrs);
+
+                dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
                 dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,
                         buf->num_pages);
-                dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+                dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->nents,
+                                   buf->dma_dir, &attrs);
                 if (buf->vaddr)
                         vm_unmap_ram(buf->vaddr, buf->num_pages);
                 sg_free_table(buf->dma_sgt);
@@ -228,6 +239,9 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
         int num_pages_from_user;
         struct vm_area_struct *vma;
         struct sg_table *sgt;
+        DEFINE_DMA_ATTRS(attrs);
+
+        dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
 
         buf = kzalloc(sizeof *buf, GFP_KERNEL);
         if (!buf)
@@ -296,9 +310,13 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
                 goto userptr_fail_alloc_table_from_pages;
 
         sgt = &buf->sg_table;
-        if (dma_map_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir) == 0)
+        /*
+         * No need to sync to the device, this will happen later when the
+         * prepare() memop is called.
+         */
+        if (dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->nents,
+                             buf->dma_dir, &attrs) == 0)
                 goto userptr_fail_map;
-        dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
         return buf;
 
 userptr_fail_map:
@@ -327,10 +345,13 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
         struct vb2_dma_sg_buf *buf = buf_priv;
         struct sg_table *sgt = &buf->sg_table;
         int i = buf->num_pages;
+        DEFINE_DMA_ATTRS(attrs);
+
+        dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
 
         dprintk(1, "%s: Releasing userspace buffer of %d pages\n",
                __func__, buf->num_pages);
-        dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+        dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir, &attrs);
         if (buf->vaddr)
                 vm_unmap_ram(buf->vaddr, buf->num_pages);
         sg_free_table(buf->dma_sgt);