Re: [PATCH v9 2/5] iommu/dma: Add a new dma_map_ops of get_merge_boundary()

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On 26/07/2019 09:31, Yoshihiro Shimoda wrote:
This patch adds a new dma_map_ops of get_merge_boundary() to
expose the DMA merge boundary if the domain type is IOMMU_DOMAIN_DMA.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Reviewed-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
---
  drivers/iommu/dma-iommu.c | 11 +++++++++++
  1 file changed, 11 insertions(+)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index a7f9c3e..2992ce4 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1085,6 +1085,16 @@ static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
  	return ret;
  }
+static unsigned long iommu_dma_get_merge_boundary(struct device *dev)
+{
+	struct iommu_domain *domain = iommu_get_dma_domain(dev);
+
+	if (domain->type != IOMMU_DOMAIN_DMA)

Did you actually need this check? In principle, if the default domain is not of type IOMMU_DOMAIN_DMA then the device should be assigned dma_direct_ops rather than iommu_dma_ops, thus it shouldn't be possible to get here. If you did manage to hit a case where the domain type didn't match the ops it would be interesting to figure out how.

Robin.

+		return 0;	/* can't merge */
+
+	return (1UL << __ffs(domain->pgsize_bitmap)) - 1;
+}
+
  static const struct dma_map_ops iommu_dma_ops = {
  	.alloc			= iommu_dma_alloc,
  	.free			= iommu_dma_free,
@@ -1100,6 +1110,7 @@ static const struct dma_map_ops iommu_dma_ops = {
  	.sync_sg_for_device	= iommu_dma_sync_sg_for_device,
  	.map_resource		= iommu_dma_map_resource,
  	.unmap_resource		= iommu_dma_unmap_resource,
+	.get_merge_boundary	= iommu_dma_get_merge_boundary,
  };
/*




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