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    SubjectRe: [PATCH v3 6/7] iommu/mediatek: Gather iova in iommu_unmap to achieve tlb sync once
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    On 2020-12-16 10:36, Yong Wu wrote:
    > In current iommu_unmap, this code is:
    >
    > iommu_iotlb_gather_init(&iotlb_gather);
    > ret = __iommu_unmap(domain, iova, size, &iotlb_gather);
    > iommu_iotlb_sync(domain, &iotlb_gather);
    >
    > We could gather the whole iova range in __iommu_unmap, and then do tlb
    > synchronization in the iommu_iotlb_sync.
    >
    > This patch implement this, Gather the range in mtk_iommu_unmap.
    > then iommu_iotlb_sync call tlb synchronization for the gathered iova range.
    > we don't call iommu_iotlb_gather_add_page since our tlb synchronization
    > could be regardless of granule size.
    >
    > In this way, gather->start is impossible ULONG_MAX, remove the checking.
    >
    > This patch aims to do tlb synchronization *once* in the iommu_unmap.

    Assuming the update to patch #4 simply results in "unsigned long end =
    iova + size - 1;" here,

    Reviewed-by: Robin Murphy <robin.murphy@arm.com>

    > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
    > ---
    > drivers/iommu/mtk_iommu.c | 8 +++++---
    > 1 file changed, 5 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
    > index db7d43adb06b..89cec51405cd 100644
    > --- a/drivers/iommu/mtk_iommu.c
    > +++ b/drivers/iommu/mtk_iommu.c
    > @@ -506,7 +506,12 @@ static size_t mtk_iommu_unmap(struct iommu_domain *domain,
    > struct iommu_iotlb_gather *gather)
    > {
    > struct mtk_iommu_domain *dom = to_mtk_domain(domain);
    > + unsigned long long end = iova + size;
    >
    > + if (gather->start > iova)
    > + gather->start = iova;
    > + if (gather->end < end)
    > + gather->end = end;
    > return dom->iop->unmap(dom->iop, iova, size, gather);
    > }
    >
    > @@ -523,9 +528,6 @@ static void mtk_iommu_iotlb_sync(struct iommu_domain *domain,
    > struct mtk_iommu_domain *dom = to_mtk_domain(domain);
    > size_t length = gather->end - gather->start;
    >
    > - if (gather->start == ULONG_MAX)
    > - return;
    > -
    > mtk_iommu_tlb_flush_range_sync(gather->start, length, gather->pgsize,
    > dom->data);
    > }
    >

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