[PATCH v2 0/6] MediaTek IOMMU improve tlb flush performance in map/unmap

Yong Wu
2020-11-19T06:18:51Z

This patchset is to improve tlb flushing performance in iommu_map/unmap
for MediaTek IOMMU.

For iommu_map, currently MediaTek IOMMU use IO_PGTABLE_QUIRK_TLBI_ON_MAP
to do tlb_flush for each a memory chunk. this is so unnecessary. we could
improve it by tlb flushing one time at the end of iommu_map.

For iommu_unmap, currently we have already improve this performance by
gather. But the current gather should take care its granule size. if the
granule size is different, it will do tlb flush and gather again. Our HW
don't care about granule size. thus I add a flag(granule_ignore) for this
case.

After this patchset, we could achieve only tlb flushing once in iommu_map
and iommu_unmap.

Regardless of sg, for each a segment, I did a simple test:

size = 20 * SZ_1M;
/* the worst case, all are 4k mapping. */
ret = iommu_map(domain, 0x5bb02000, 0x123f1000, size, IOMMU_READ);
iommu_unmap(domain, 0x5bb02000, size);

This is the comparing time(unit is us):
original-time after-improve
map-20M 59943 2347
unmap-20M 264 36

This patchset also flush tlb once in the iommu_map_sg case.

patch [1/6][2/6][3/6] are for map while the others are for unmap.

change note:
v2: Refactor all the code.
base on v5.10-rc1.

v1: https://lore.kernel.org/linux-iommu/20201019113100.23661-1-chao.hao@mediatek.com/

Yong Wu (6):
iommu: Move iotlb_sync_map out from __iommu_map
iommu: Add iova and size as parameters in iommu_iotlb_map
iommu/mediatek: Add iotlb_sync_map to sync whole the iova range
iommu: Add granule_ignore when tlb gather
iommu/mediatek: Enable granule_ignore for unmap
iommu/mediatek: Convert tlb_flush_walk to gather_add_page

drivers/iommu/iommu.c | 24 +++++++++++++++++++-----
drivers/iommu/mtk_iommu.c | 32 ++++++++++++++++++++++++++------
drivers/iommu/tegra-gart.c | 3 ++-
include/linux/iommu.h | 7 +++++--
4 files changed, 52 insertions(+), 14 deletions(-)

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2.18.0