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Subject[PATCH v2 8/8] iommu/tegra: gart: Optimize mapping / unmapping performance
Date
Currently GART writes one page entry at a time. More optimal would be to
aggregate the writes and flush BUS buffer in the end, this gives map/unmap
10-40% performance boost (depending on size of mapping) in comparison to
flushing after each page entry update.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/iommu/tegra-gart.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c
index bcdb8973a0ad..5e3fd32fce4a 100644
--- a/drivers/iommu/tegra-gart.c
+++ b/drivers/iommu/tegra-gart.c
@@ -293,7 +293,6 @@ static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova,
}
}
gart_set_pte(gart, iova, GART_PTE(pfn));
- FLUSH_GART_REGS(gart);
spin_unlock_irqrestore(&gart->pte_lock, flags);
return 0;
}
@@ -310,7 +309,6 @@ static size_t gart_iommu_unmap(struct iommu_domain *domain, unsigned long iova,

spin_lock_irqsave(&gart->pte_lock, flags);
gart_set_pte(gart, iova, 0);
- FLUSH_GART_REGS(gart);
spin_unlock_irqrestore(&gart->pte_lock, flags);
return bytes;
}
@@ -376,6 +374,14 @@ static int gart_iommu_of_xlate(struct device *dev,
return 0;
}

+static void gart_iommu_sync(struct iommu_domain *domain)
+{
+ struct gart_domain *gart_domain = to_gart_domain(domain);
+ struct gart_device *gart = gart_domain->gart;
+
+ FLUSH_GART_REGS(gart);
+}
+
static const struct iommu_ops gart_iommu_ops = {
.capable = gart_iommu_capable,
.domain_alloc = gart_iommu_domain_alloc,
@@ -391,6 +397,8 @@ static const struct iommu_ops gart_iommu_ops = {
.iova_to_phys = gart_iommu_iova_to_phys,
.pgsize_bitmap = GART_IOMMU_PGSIZES,
.of_xlate = gart_iommu_of_xlate,
+ .iotlb_sync_map = gart_iommu_sync,
+ .iotlb_sync = gart_iommu_sync,
};

static int tegra_gart_suspend(struct device *dev)
--
2.18.0
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