The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. Adapt the code to obey those rules.

Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com>
---
For more information, see '[PATCH v2 00/21] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/4/373
---
 drivers/gpu/host1x/job.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/host1x/job.c b/drivers/gpu/host1x/job.c
index a10643a..3ea185e 100644
--- a/drivers/gpu/host1x/job.c
+++ b/drivers/gpu/host1x/job.c
@@ -166,8 +166,9 @@ 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) {
+                       sgt->nents = dma_map_sg(dev, sgt->sgl, sgt->orig_nents,
+                                               dir);
+                       if (!sgt->nents) {
                                err = -ENOMEM;
                                goto unpin;
                        }
@@ -217,7 +218,7 @@ static unsigned int pin_job(struct host1x *host, struct 
host1x_job *job)
                }
 
                if (!IS_ENABLED(CONFIG_TEGRA_HOST1X_FIREWALL) && host->domain) {
-                       for_each_sg(sgt->sgl, sg, sgt->nents, j)
+                       for_each_sg(sgt->sgl, sg, sgt->orig_nents, j)
                                gather_size += sg->length;
                        gather_size = iova_align(&host->iova, gather_size);
 
@@ -231,7 +232,7 @@ static unsigned int pin_job(struct host1x *host, struct 
host1x_job *job)
 
                        err = iommu_map_sg(host->domain,
                                        iova_dma_addr(&host->iova, alloc),
-                                       sgt->sgl, sgt->nents, IOMMU_READ);
+                                       sgt->sgl, sgt->orig_nents, IOMMU_READ);
                        if (err == 0) {
                                __free_iova(&host->iova, alloc);
                                err = -EINVAL;
@@ -241,9 +242,9 @@ 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) {
+                       sgt->nents = dma_map_sg(host->dev, sgt->sgl,
+                                               sgt->orig_nents, DMA_TO_DEVICE);
+                       if (!sgt->nents) {
                                err = -ENOMEM;
                                goto unpin;
                        }
@@ -647,7 +648,7 @@ void host1x_job_unpin(struct host1x_job *job)
                }
 
                if (unpin->dev && sgt)
-                       dma_unmap_sg(unpin->dev, sgt->sgl, sgt->nents,
+                       dma_unmap_sg(unpin->dev, sgt->sgl, sgt->orig_nents,
                                     unpin->dir);
 
                host1x_bo_unpin(dev, unpin->bo, sgt);
-- 
1.9.1

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