linux-kernel - [PATCH v4 6/7] iommu/mediatek: Gather iova in iommu

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Date:   Thu, 7 Jan 2021 20:29:08 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Tomasz Figa <tfiga@...gle.com>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <yong.wu@...iatek.com>,
        <youlin.pei@...iatek.com>, Nicolas Boichat <drinkcat@...omium.org>,
        <anan.sun@...iatek.com>, <chao.hao@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...gle.com>,
        <kernel-team@...roid.com>, Christoph Hellwig <hch@...radead.org>,
        David Laight <David.Laight@...LAB.COM>
Subject: [PATCH v4 6/7] iommu/mediatek: Gather iova in iommu_unmap to achieve tlb sync once

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.

Signed-off-by: Yong Wu <yong.wu@...iatek.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 66a00a2cb445..d3b8a1649093 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -430,7 +430,12 @@ 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 end = iova + size - 1;
 
+	if (gather->start > iova)
+		gather->start = iova;
+	if (gather->end < end)
+		gather->end = end;
 	return dom->iop->unmap(dom->iop, iova, size, gather);
 }
 
@@ -445,9 +450,6 @@ static void mtk_iommu_iotlb_sync(struct iommu_domain *domain,
 	struct mtk_iommu_data *data = mtk_iommu_get_m4u_data();
 	size_t length = gather->end - gather->start + 1;
 
-	if (gather->start == ULONG_MAX)
-		return;
-
 	mtk_iommu_tlb_flush_range_sync(gather->start, length, gather->pgsize,
 				       data);
 }
-- 
2.18.0