[PATCH v3 3/7] iommu/mediatek: Use gather to achieve the tlb range flush

[Yong Wu]

Use the iommu_gather mechanism to achieve the tlb range flush.
Gather the iova range in the "tlb_add_page", then flush the merged iova
range in iotlb_sync.

Note: If iotlb_sync comes from iommu_iotlb_gather_add_page, we have to
avoid retry the lock since the spinlock have already been acquired.

Suggested-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
---
1) This is the special case backtrace:

 mtk_iommu_iotlb_sync+0x50/0xa0
 mtk_iommu_tlb_flush_page_nosync+0x5c/0xd0
 __arm_v7s_unmap+0x174/0x598
 arm_v7s_unmap+0x30/0x48
 mtk_iommu_unmap+0x50/0x78
 __iommu_unmap+0xa4/0xf8

2) The checking "if (gather->start == ULONG_MAX) return;" also is
necessary. It will happened when unmap only go to _flush_walk, then
enter this tlb_sync.
---
 drivers/iommu/mtk_iommu.c | 29 +++++++++++++++++++++++++----
 drivers/iommu/mtk_iommu.h |  1 +
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 5f594d6..8712afc 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -234,7 +234,12 @@ static void mtk_iommu_tlb_flush_page_nosync(struct iommu_iotlb_gather *gather,
 					    unsigned long iova, size_t granule,
 					    void *cookie)
 {
-	mtk_iommu_tlb_add_flush_nosync(iova, granule, granule, true, cookie);
+	struct mtk_iommu_data *data = cookie;
+	struct iommu_domain *domain = &data->m4u_dom->domain;
+
+	data->is_in_tlb_gather_add_page = true;
+	iommu_iotlb_gather_add_page(domain, gather, iova, granule);
+	data->is_in_tlb_gather_add_page = false;
 }
 
 static const struct iommu_flush_ops mtk_iommu_flush_ops = {
@@ -453,12 +458,28 @@ static void mtk_iommu_flush_iotlb_all(struct iommu_domain *domain)
 static void mtk_iommu_iotlb_sync(struct iommu_domain *domain,
 				 struct iommu_iotlb_gather *gather)
 {
+	struct mtk_iommu_data *data = mtk_iommu_get_m4u_data();
 	struct mtk_iommu_domain *dom = to_mtk_domain(domain);
+	bool is_in_gather = data->is_in_tlb_gather_add_page;
+	size_t length = gather->end - gather->start;
 	unsigned long flags;
 
-	spin_lock_irqsave(&dom->pgtlock, flags);
-	mtk_iommu_tlb_sync(mtk_iommu_get_m4u_data());
-	spin_unlock_irqrestore(&dom->pgtlock, flags);
+	if (gather->start == ULONG_MAX)
+		return;
+
+	/*
+	 * Avoid acquire the lock when it's in gather_add_page since the lock
+	 * has already been held.
+	 */
+	if (!is_in_gather)
+		spin_lock_irqsave(&dom->pgtlock, flags);
+
+	mtk_iommu_tlb_add_flush_nosync(gather->start, length, gather->pgsize,
+				       false, data);
+	mtk_iommu_tlb_sync(data);
+
+	if (!is_in_gather)
+		spin_unlock_irqrestore(&dom->pgtlock, flags);
 }
 
 static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
index fc0f16e..d29af1d 100644
--- a/drivers/iommu/mtk_iommu.h
+++ b/drivers/iommu/mtk_iommu.h
@@ -58,6 +58,7 @@ struct mtk_iommu_data {
 	struct iommu_group		*m4u_group;
 	bool                            enable_4GB;
 	bool				tlb_flush_active;
+	bool				is_in_tlb_gather_add_page;
 
 	struct iommu_device		iommu;
 	const struct mtk_iommu_plat_data *plat_data;
-- 
1.9.1