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* [PATCH] drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1
@ 2017-11-01 14:14 ` Liviu Dudau
  0 siblings, 0 replies; 16+ messages in thread
From: Liviu Dudau @ 2017-11-01 14:14 UTC (permalink / raw)
  To: Brian Starkey
  Cc: Mali DP Maintainers, Daniel Vetter, David Airlie, DRI-devel,
	LKML, Jani Nikula, Sean Paul, Liviu Dudau

drm_gem_cma_prime_import_sg_table() will fail if the number of entries
in the sg_table > 1. However, you can have a device that uses an IOMMU
engine and can map a discontiguous buffer with multiple entries that
have consecutive sg_dma_addresses, effectively making it contiguous.
Allow for that scenario by testing the entries in the sg_table for
contiguous coverage.

Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
---

Hi,

This patch is the only change I need in order to be able to use existing
IOMMU domain infrastructure with the Mali DP driver. I have tested the
patch and I know it works correctly for my setup, but I would like to get
some comments on whether I am on the right path or if CMA really wants to
see an sg_table with only one entry.

Best regards,
Liviu

 drivers/gpu/drm/drm_gem_cma_helper.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index 020e7668dfaba..43b179212052d 100644
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -482,8 +482,26 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev,
 {
 	struct drm_gem_cma_object *cma_obj;
 
-	if (sgt->nents != 1)
-		return ERR_PTR(-EINVAL);
+	if (sgt->nents != 1) {
+		/* check if the entries in the sg_table are contiguous */
+		dma_addr_t next_addr = sg_dma_address(sgt->sgl);
+		struct scatterlist *s;
+		unsigned int i;
+
+		for_each_sg(sgt->sgl, s, sgt->nents, i) {
+			/*
+			 * sg_dma_address(s) is only valid for entries
+			 * that have sg_dma_len(s) != 0
+			 */
+			if (!sg_dma_len(s))
+				continue;
+
+			if (sg_dma_address(s) != next_addr)
+				return ERR_PTR(-EINVAL);
+
+			next_addr = sg_dma_address(s) + sg_dma_len(s);
+		}
+	}
 
 	/* Create a CMA GEM buffer. */
 	cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size);
-- 
2.14.3

^ permalink raw reply related	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2017-11-15 14:41 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-11-01 14:14 [PATCH] drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1 Liviu Dudau
2017-11-01 14:14 ` Liviu Dudau
2017-11-10  4:26 ` Laurent Pinchart
2017-11-10  4:26   ` Laurent Pinchart
2017-11-10 13:33   ` [PATCH v2] " Liviu Dudau
2017-11-10 13:33     ` Liviu Dudau
2017-11-11 12:47     ` Laurent Pinchart
2017-11-11 12:47       ` Laurent Pinchart
2017-11-15 13:04       ` Liviu Dudau
2017-11-15 13:04         ` Liviu Dudau
2017-11-15 14:24         ` Noralf Trønnes
2017-11-15 14:24           ` Noralf Trønnes
2017-11-15 14:41           ` Liviu Dudau
2017-11-15 14:41             ` Liviu Dudau
2017-11-10 14:19 ` ✓ Fi.CI.BAT: success for " Patchwork
2017-11-10 16:10 ` ✓ Fi.CI.IGT: " Patchwork

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