Hi,

On Wed, Mar 2, 2016 at 10:54 AM, Yong Wu [off-list ref] wrote:

Sometimes it is not worth for the iommu allocating big chunks.
Here we enable DMA_ATTR_ALLOC_SINGLE_PAGES which could help avoid to
allocate big chunks while iommu allocating buffer.

More information about this attribute, please check Doug's commit[1].

[1]: https://lkml.org/lkml/2016/1/11/720

Cc: Robin Murphy <robin.murphy@arm.com>
Suggested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
---

Our video drivers may soon use this.

 arch/arm64/mm/dma-mapping.c |  4 ++--
 drivers/iommu/dma-iommu.c   | 14 ++++++++++----
 include/linux/dma-iommu.h   |  4 ++--
 3 files changed, 14 insertions(+), 8 deletions(-)

It should also be mentioned that this depends on commit df05c6f6e0bb
("ARM: 8506/1: common: DMA-mapping: add DMA_ATTR_ALLOC_SINGLE_PAGES
attribute") which is not in mainline quite yet.

Also please CC Marek Szyprowski on any future patches in this area
since I saw a patch series from him that was touching this same area.

Reviewed-by: Douglas Anderson <dianders@chromium.org>