diff mbox series

[v10,03/30] drm: core: fix common struct sg_table related issues

Message ID 20200904131711.12950-4-m.szyprowski@samsung.com
State New, archived
Headers show
Series [v10,01/30] drm: prime: add common helper to check scatterlist contiguity | expand

Commit Message

Marek Szyprowski Sept. 4, 2020, 1:16 p.m. UTC
The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()

To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
 drivers/gpu/drm/drm_cache.c            |  2 +-
 drivers/gpu/drm/drm_gem_shmem_helper.c | 14 +++++++++-----
 drivers/gpu/drm/drm_prime.c            | 11 ++++++-----
 3 files changed, 16 insertions(+), 11 deletions(-)
diff mbox series


diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c
index 03e01b000f7a..0fe3c496002a 100644
--- a/drivers/gpu/drm/drm_cache.c
+++ b/drivers/gpu/drm/drm_cache.c
@@ -127,7 +127,7 @@  drm_clflush_sg(struct sg_table *st)
 		struct sg_page_iter sg_iter;
 		mb(); /*CLFLUSH is ordered only by using memory barriers*/
-		for_each_sg_page(st->sgl, &sg_iter, st->nents, 0)
+		for_each_sgtable_page(st, &sg_iter, 0)
 		mb(); /*Make sure that all cache line entry is flushed*/
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 4b7cfbac4daa..47d8211221f2 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -126,8 +126,8 @@  void drm_gem_shmem_free_object(struct drm_gem_object *obj)
 		drm_prime_gem_destroy(obj, shmem->sgt);
 	} else {
 		if (shmem->sgt) {
-			dma_unmap_sg(obj->dev->dev, shmem->sgt->sgl,
-				     shmem->sgt->nents, DMA_BIDIRECTIONAL);
+			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
@@ -424,8 +424,7 @@  void drm_gem_shmem_purge_locked(struct drm_gem_object *obj)
-	dma_unmap_sg(obj->dev->dev, shmem->sgt->sgl,
-		     shmem->sgt->nents, DMA_BIDIRECTIONAL);
+	dma_unmap_sgtable(obj->dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
 	shmem->sgt = NULL;
@@ -697,12 +696,17 @@  struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj)
 		goto err_put_pages;
 	/* Map the pages for use by the h/w. */
-	dma_map_sg(obj->dev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL);
+	ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
+	if (ret)
+		goto err_free_sgt;
 	shmem->sgt = sgt;
 	return sgt;
+	sg_free_table(sgt);
+	kfree(sgt);
 	return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index c5e796d4a489..b8c7f068a5a4 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -617,6 +617,7 @@  struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach,
 	struct drm_gem_object *obj = attach->dmabuf->priv;
 	struct sg_table *sgt;
+	int ret;
 	if (WARN_ON(dir == DMA_NONE))
 		return ERR_PTR(-EINVAL);
@@ -626,11 +627,12 @@  struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach,
 		sgt = obj->dev->driver->gem_prime_get_sg_table(obj);
-	if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
-			      DMA_ATTR_SKIP_CPU_SYNC)) {
+	ret = dma_map_sgtable(attach->dev, sgt, dir,
+	if (ret) {
-		sgt = ERR_PTR(-ENOMEM);
+		sgt = ERR_PTR(ret);
 	return sgt;
@@ -652,8 +654,7 @@  void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
 	if (!sgt)
-	dma_unmap_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
+	dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC);