[PATCH v3 6/7] iommu/mediatek: Gather iova in iommu_unmap to achieve tlb sync once

[Will Deacon]

On Mon, Jan 18, 2021 at 04:35:22PM +0000, Robin Murphy wrote:
> 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 at arm.com>

There's a v4 here:

https://lore.kernel.org/r/20210107122909.16317-1-yong.wu@mediatek.com

Will