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drm: lima: 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 <m.szyprowski@samsung.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
This commit is contained in:
Marek Szyprowski 2020-04-28 13:09:11 +02:00
parent b827e3ac41
commit c3d9c17f48
2 changed files with 10 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
drivers/gpu/drm/lima/lima_gem.c
View File

@ -69,8 +69,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
return ret;
if (bo->base.sgt) {
dma_unmap_sg(dev, bo->base.sgt->sgl,
bo->base.sgt->nents, DMA_BIDIRECTIONAL);
dma_unmap_sgtable(dev, bo->base.sgt, DMA_BIDIRECTIONAL, 0);
sg_free_table(bo->base.sgt);
} else {
bo->base.sgt = kmalloc(sizeof(*bo->base.sgt), GFP_KERNEL);
@ -80,7 +79,13 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
}
}
dma_map_sg(dev, sgt.sgl, sgt.nents, DMA_BIDIRECTIONAL);
ret = dma_map_sgtable(dev, &sgt, DMA_BIDIRECTIONAL, 0);
if (ret) {
sg_free_table(&sgt);
kfree(bo->base.sgt);
bo->base.sgt = NULL;
return ret;
}
*bo->base.sgt = sgt;

5
drivers/gpu/drm/lima/lima_vm.c
View File

@ -124,7 +124,7 @@ int lima_vm_bo_add(struct lima_vm *vm, struct lima_bo *bo, bool create)
if (err)
goto err_out1;
for_each_sg_dma_page(bo->base.sgt->sgl, &sg_iter, bo->base.sgt->nents, 0) {
for_each_sgtable_dma_page(bo->base.sgt, &sg_iter, 0) {
err = lima_vm_map_page(vm, sg_page_iter_dma_address(&sg_iter),
bo_va->node.start + offset);
if (err)
@ -298,8 +298,7 @@ int lima_vm_map_bo(struct lima_vm *vm, struct lima_bo *bo, int pageoff)
mutex_lock(&vm->lock);
base = bo_va->node.start + (pageoff << PAGE_SHIFT);
for_each_sg_dma_page(bo->base.sgt->sgl, &sg_iter,
bo->base.sgt->nents, pageoff) {
for_each_sgtable_dma_page(bo->base.sgt, &sg_iter, pageoff) {
err = lima_vm_map_page(vm, sg_page_iter_dma_address(&sg_iter),
base + offset);
if (err)