Hi,
On 2019-06-20 10:50, 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>
> ---
> 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 205d694..9950cb5 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1091,6 +1091,16 @@ 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)
> + return 0; /* can't merge */
> +
> + return (1 << __ffs(domain->pgsize_bitmap)) - 1;
> +}
I really wonder if there is any IOMMU, which doesn't support 4KiB pages.
Cannot you simply assume that the merge boundary is 4KiB and avoid
adding this new API?
> +
> static const struct dma_map_ops iommu_dma_ops = {
> .alloc = iommu_dma_alloc,
> .free = iommu_dma_free,
> @@ -1106,6 +1116,7 @@ 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,
> };
>
> /*
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
