[PATCH v2 3/3] drm/radeon: Allow dma_map_sg() coalescing

Robin Murphy robin.murphy at arm.com
Tue Apr 17 15:58:15 UTC 2018

Much like amdgpu, the radeon driver doesn't appear to directly use the
scatterlist mapped by radeon_ttm_tt_pin_userptr(), it merely hands it
off to drm_prime_sg_to_page_addr_arrays() to generate the dma_address
array which it actually cares about. Now that the latter can cope with
dma_map_sg() coalescing dma-contiguous segments such that it returns
0 < count < nents, we can relax the current count == nents check to
only consider genuine failure as other drivers do.

Suggested-by: Christian K├Ânig <christian.koenig at amd.com>
Signed-off-by: Robin Murphy <robin.murphy at arm.com>

v2: New

 drivers/gpu/drm/radeon/radeon_ttm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 8689fcca051c..7c099192c7fa 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -585,7 +585,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 	r = -ENOMEM;
 	nents = dma_map_sg(rdev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
-	if (nents != ttm->sg->nents)
+	if (nents == 0)
 		goto release_sg;
 	drm_prime_sg_to_page_addr_arrays(ttm->sg, ttm->pages,

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