drm: host1x: 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: Robin Murphy <robin.murphy@arm.com>

diff --git a/drivers/gpu/host1x/job.c b/drivers/gpu/host1x/job.c
index 89b6c14b7392022164ede57a0f3095f360476b8a..82d0a60ba3f770be7d81025fa612e57c79b98a76 100644 (file)
--- a/drivers/gpu/host1x/job.c
+++ b/drivers/gpu/host1x/job.c
@@ -170,11 +170,9 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
                                goto unpin;
                        }
 
-                       err = dma_map_sg(dev, sgt->sgl, sgt->nents, dir);
-                       if (!err) {
-                               err = -ENOMEM;
+                       err = dma_map_sgtable(dev, sgt, dir, 0);
+                       if (err)
                                goto unpin;
-                       }
 
                        job->unpins[job->num_unpins].dev = dev;
                        job->unpins[job->num_unpins].dir = dir;
@@ -228,7 +226,7 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
                }
 
                if (host->domain) {
-                       for_each_sg(sgt->sgl, sg, sgt->nents, j)
+                       for_each_sgtable_sg(sgt, sg, j)
                                gather_size += sg->length;
                        gather_size = iova_align(&host->iova, gather_size);
 
@@ -240,9 +238,9 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
                                goto put;
                        }
 
-                       err = iommu_map_sg(host->domain,
+                       err = iommu_map_sgtable(host->domain,
                                        iova_dma_addr(&host->iova, alloc),
-                                       sgt->sgl, sgt->nents, IOMMU_READ);
+                                       sgt, IOMMU_READ);
                        if (err == 0) {
                                __free_iova(&host->iova, alloc);
                                err = -EINVAL;
@@ -252,12 +250,9 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
                        job->unpins[job->num_unpins].size = gather_size;
                        phys_addr = iova_dma_addr(&host->iova, alloc);
                } else if (sgt) {
-                       err = dma_map_sg(host->dev, sgt->sgl, sgt->nents,
-                                        DMA_TO_DEVICE);
-                       if (!err) {
-                               err = -ENOMEM;
+                       err = dma_map_sgtable(host->dev, sgt, DMA_TO_DEVICE, 0);
+                       if (err)
                                goto put;
-                       }
 
                        job->unpins[job->num_unpins].dir = DMA_TO_DEVICE;
                        job->unpins[job->num_unpins].dev = host->dev;
@@ -660,8 +655,7 @@ void host1x_job_unpin(struct host1x_job *job)
                }
 
                if (unpin->dev && sgt)
-                       dma_unmap_sg(unpin->dev, sgt->sgl, sgt->nents,
-                                    unpin->dir);
+                       dma_unmap_sgtable(unpin->dev, sgt, unpin->dir, 0);
 
                host1x_bo_unpin(dev, unpin->bo, sgt);
                host1x_bo_put(unpin->bo);