[PATCH v3 3/6] iommu: Improve iommu_iotlb_gather helpers

[Nadav Amit <nadav.amit@gmail.com>]

From: Robin Murphy <robin.murphy@arm.com>

The Mediatek driver is not the only one which might want a basic
address-based gathering behaviour, so although it's arguably simple
enough to open-code, let's factor it out for the sake of cleanliness.
Let's also take this opportunity to document the intent of these
helpers for clarity.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Cc: Jiajun Cao <caojiajun@vmware.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Robin Murphy <robin.murphy@arm.com>

---

Changes from Robin's version:
* Added iommu_iotlb_gather_add_range() stub !CONFIG_IOMMU_API
* Use iommu_iotlb_gather_add_range() in iommu_iotlb_gather_add_page()
---
 drivers/iommu/mtk_iommu.c |  5 +----
 include/linux/iommu.h     | 43 ++++++++++++++++++++++++++++++++++-----
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index e06b8a0e2b56..0af4a91ac7da 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -523,10 +523,7 @@ static size_t mtk_iommu_unmap(struct iommu_domain *domain,
 	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;
+	iommu_iotlb_gather_add_range(gather, iova, size);
 	return dom->iop->unmap(dom->iop, iova, size, gather);
 }
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 32d448050bf7..f254c62f3720 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -497,6 +497,38 @@ static inline void iommu_iotlb_sync(struct iommu_domain *domain,
 	iommu_iotlb_gather_init(iotlb_gather);
 }
 
+/**
+ * iommu_iotlb_gather_add_range - Gather for address-based TLB invalidation
+ * @gather: TLB gather data
+ * @iova: start of page to invalidate
+ * @size: size of page to invalidate
+ *
+ * Helper for IOMMU drivers to build arbitrarily-sized invalidation commands
+ * where only the address range matters, and simply minimising intermediate
+ * syncs is preferred.
+ */
+static inline void iommu_iotlb_gather_add_range(struct iommu_iotlb_gather *gather,
+						unsigned long iova, size_t size)
+{
+	unsigned long end = iova + size - 1;
+
+	if (gather->start > iova)
+		gather->start = iova;
+	if (gather->end < end)
+		gather->end = end;
+}
+
+/**
+ * iommu_iotlb_gather_add_page - Gather for page-based TLB invalidation
+ * @domain: IOMMU domain to be invalidated
+ * @gather: TLB gather data
+ * @iova: start of page to invalidate
+ * @size: size of page to invalidate
+ *
+ * Helper for IOMMU drivers to build invalidation commands based on individual
+ * pages, or with page size/table level hints which cannot be gathered if they
+ * differ.
+ */
 static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 					       struct iommu_iotlb_gather *gather,
 					       unsigned long iova, size_t size)
@@ -515,11 +547,7 @@ static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 		gather->pgsize = size;
 	}
 
-	if (gather->end < end)
-		gather->end = end;
-
-	if (gather->start > start)
-		gather->start = start;
+	iommu_iotlb_gather_add_range(gather, iova, size);
 }
 
 /* PCI device grouping function */
@@ -702,6 +730,11 @@ static inline void iommu_iotlb_sync(struct iommu_domain *domain,
 {
 }
 
+static inline void iommu_iotlb_gather_add_range(struct iommu_iotlb_gather *gather,
+						unsigned long iova, size_t size)
+{
+}
+
 static inline phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, dma_addr_t iova)
 {
 	return 0;
-- 
2.25.1