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drm: rockchip: fix common struct sg_table related issues

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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()
function.

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: Robin Murphy <robin.murphy@arm.com>
This commit is contained in:
Marek Szyprowski 2020-04-28 13:10:01 +02:00
parent 6a8f15c62c
commit 82c245b592
1 changed files with 10 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/gpu/drm/rockchip/rockchip_drm_gem.c
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@ -36,8 +36,8 @@ static int rockchip_gem_iommu_map(struct rockchip_gem_object *rk_obj)
rk_obj->dma_addr = rk_obj->mm.start;
ret = iommu_map_sg(private->domain, rk_obj->dma_addr, rk_obj->sgt->sgl,
rk_obj->sgt->nents, prot);
ret = iommu_map_sgtable(private->domain, rk_obj->dma_addr, rk_obj->sgt,
prot);
if (ret < rk_obj->base.size) {
DRM_ERROR("failed to map buffer: size=%zd request_size=%zd\n",
ret, rk_obj->base.size);
@ -98,11 +98,10 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj)
* TODO: Replace this by drm_clflush_sg() once it can be implemented
* without relying on symbols that are not exported.
*/
for_each_sg(rk_obj->sgt->sgl, s, rk_obj->sgt->nents, i)
for_each_sgtable_sg(rk_obj->sgt, s, i)
sg_dma_address(s) = sg_phys(s);
dma_sync_sg_for_device(drm->dev, rk_obj->sgt->sgl, rk_obj->sgt->nents,
DMA_TO_DEVICE);
dma_sync_sgtable_for_device(drm->dev, rk_obj->sgt, DMA_TO_DEVICE);
return 0;
@ -350,8 +349,8 @@ void rockchip_gem_free_object(struct drm_gem_object *obj)
if (private->domain) {
rockchip_gem_iommu_unmap(rk_obj);
} else {
dma_unmap_sg(drm->dev, rk_obj->sgt->sgl,
rk_obj->sgt->nents, DMA_BIDIRECTIONAL);
dma_unmap_sgtable(drm->dev, rk_obj->sgt,
DMA_BIDIRECTIONAL, 0);
}
drm_prime_gem_destroy(obj, rk_obj->sgt);
} else {
@ -476,15 +475,13 @@ rockchip_gem_dma_map_sg(struct drm_device *drm,
struct sg_table *sg,
struct rockchip_gem_object *rk_obj)
{
int count = dma_map_sg(drm->dev, sg->sgl, sg->nents,
DMA_BIDIRECTIONAL);
if (!count)
return -EINVAL;
int err = dma_map_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0);
if (err)
return err;
if (drm_prime_get_contiguous_size(sg) < attach->dmabuf->size) {
DRM_ERROR("failed to map sg_table to contiguous linear address.\n");
dma_unmap_sg(drm->dev, sg->sgl, sg->nents,
DMA_BIDIRECTIONAL);
dma_unmap_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0);
return -EINVAL;
}