drm: amdgpu: fix common struct sg_table related issues

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 <[email protected]>
Reviewed-by: Christian König <[email protected]>
Link: https://patchwork.freedesktop.org/patch/371142/
Signed-off-by: Christian König <[email protected]>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
index 43d8ed7dbd0018d66192e43f487f5aadc814fc4c..519ce4427fcedcdc89d46fff45b5fbb110cc36a1 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
@@ -307,8 +307,8 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
                if (IS_ERR(sgt))
                        return sgt;
 
-               if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
-                                     DMA_ATTR_SKIP_CPU_SYNC))
+               if (dma_map_sgtable(attach->dev, sgt, dir,
+                                   DMA_ATTR_SKIP_CPU_SYNC))
                        goto error_free;
                break;
 
@@ -349,7 +349,7 @@ static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach,
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
 
        if (sgt->sgl->page_link) {
-               dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+               dma_unmap_sgtable(attach->dev, sgt, dir, 0);
                sg_free_table(sgt);
                kfree(sgt);
        } else {

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 38d2a7fb5698a27d5f3ed0f08ecea85169196fc8..4223c56188fe506b7f14e8257f1563d051300728 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1043,7 +1043,6 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 {
        struct amdgpu_device *adev = amdgpu_ttm_adev(ttm->bdev);
        struct amdgpu_ttm_tt *gtt = (void *)ttm;
-       unsigned nents;
        int r;
 
        int write = !(gtt->userflags & AMDGPU_GEM_USERPTR_READONLY);
@@ -1058,9 +1057,8 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
                goto release_sg;
 
        /* Map SG to device */
-       r = -ENOMEM;
-       nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
-       if (nents == 0)
+       r = dma_map_sgtable(adev->dev, ttm->sg, direction, 0);
+       if (r)
                goto release_sg;
 
        /* convert SG to linear array of pages and dma addresses */
@@ -1091,8 +1089,7 @@ static void amdgpu_ttm_tt_unpin_userptr(struct ttm_tt *ttm)
                return;
 
        /* unmap the pages mapped to the device */
-       dma_unmap_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
-
+       dma_unmap_sgtable(adev->dev, ttm->sg, direction, 0);
        sg_free_table(ttm->sg);
 
 #if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index ad5732f8d4d2460c508e39ca1ae4a918bba7dafe..d4f626d9bec1829c5d61738567dc0343c6423416 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -476,11 +476,11 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
        if (r)
                goto error_free;
 
-       for_each_sg((*sgt)->sgl, sg, num_entries, i)
+       for_each_sgtable_sg((*sgt), sg, i)
                sg->length = 0;
 
        node = mem->mm_node;
-       for_each_sg((*sgt)->sgl, sg, num_entries, i) {
+       for_each_sgtable_sg((*sgt), sg, i) {
                phys_addr_t phys = (node->start << PAGE_SHIFT) +
                        adev->gmc.aper_base;
                size_t size = node->size << PAGE_SHIFT;
@@ -500,7 +500,7 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
        return 0;
 
 error_unmap:
-       for_each_sg((*sgt)->sgl, sg, num_entries, i) {
+       for_each_sgtable_sg((*sgt), sg, i) {
                if (!sg->length)
                        continue;
 
@@ -531,7 +531,7 @@ void amdgpu_vram_mgr_free_sgt(struct amdgpu_device *adev,
        struct scatterlist *sg;
        int i;
 
-       for_each_sg(sgt->sgl, sg, sgt->nents, i)
+       for_each_sgtable_sg(sgt, sg, i)
                dma_unmap_resource(dev, sg->dma_address,
                                   sg->length, dir,
                                   DMA_ATTR_SKIP_CPU_SYNC);