[RFC 16/17] drm: host1x: fix sg_table nents vs. orig_nents misuse

From: Marek Szyprowski
Date: Tue Apr 28 2020 - 09:20:48 EST


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.szyprowski@xxxxxxxxxxx>
---
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