[PATCH V2 3/6] iommu: iova: add support for 'first-fit' algorithm

[Ajay Kumar]

From: Marek Szyprowski <m.szyprowski at samsung.com>

Add support for the 'first-fit' allocation algorithm. It will be used for
the special case of implementing DMA_ATTR_LOW_ADDRESS, so this path
doesn't use IOVA cache.

Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
Signed-off-by: Ajay Kumar <ajaykumar.rs at samsung.com>
---
 drivers/iommu/iova.c | 78 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/iova.h |  2 ++
 2 files changed, 80 insertions(+)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index ae0fe0a6714e..89f9338f83a3 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -231,6 +231,59 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	return -ENOMEM;
 }
 
+static unsigned long
+__iova_get_aligned_start(unsigned long start, unsigned long size)
+{
+	unsigned long mask = __roundup_pow_of_two(size) - 1;
+
+	return (start + mask) & ~mask;
+}
+
+static int __alloc_and_insert_iova_range_forward(struct iova_domain *iovad,
+			unsigned long size, unsigned long limit_pfn,
+			struct iova *new)
+{
+	struct rb_node *curr;
+	unsigned long flags;
+	unsigned long start, limit;
+
+	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+
+	curr = rb_first(&iovad->rbroot);
+	limit = limit_pfn;
+	start = __iova_get_aligned_start(iovad->start_pfn, size);
+
+	while (curr) {
+		struct iova *curr_iova = rb_entry(curr, struct iova, node);
+		struct rb_node *next = rb_next(curr);
+
+		start = __iova_get_aligned_start(curr_iova->pfn_hi + 1, size);
+		if (next) {
+			struct iova *next_iova = rb_entry(next, struct iova, node);
+			limit = next_iova->pfn_lo - 1;
+		} else {
+			limit = limit_pfn;
+		}
+
+		if ((start + size) <= limit)
+			break;	/* found a free slot */
+		curr = next;
+	}
+
+	if (!curr && start + size > limit) {
+		spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+		return -ENOMEM;
+	}
+
+	new->pfn_lo = start;
+	new->pfn_hi = new->pfn_lo + size - 1;
+	iova_insert_rbtree(&iovad->rbroot, new, curr);
+
+	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+
+	return 0;
+}
+
 static struct kmem_cache *iova_cache;
 static unsigned int iova_cache_users;
 static DEFINE_MUTEX(iova_cache_mutex);
@@ -420,6 +473,31 @@ free_iova(struct iova_domain *iovad, unsigned long pfn)
 }
 EXPORT_SYMBOL_GPL(free_iova);
 
+/**
+ * alloc_iova_first_fit - allocates an iova from the beginning of address space
+ * @iovad: - iova domain in question
+ * @size: - size of page frames to allocate
+ * @limit_pfn: - max limit address
+ * Returns a pfn the allocated iova starts at or IOVA_BAD_ADDR in the case
+ * of a failure.
+ */
+unsigned long
+alloc_iova_first_fit(struct iova_domain *iovad, unsigned long size,
+		     unsigned long limit_pfn)
+{
+	struct iova *new_iova = alloc_iova_mem();
+
+	if (!new_iova)
+		return IOVA_BAD_ADDR;
+
+	if (__alloc_and_insert_iova_range_forward(iovad, size, limit_pfn, new_iova)) {
+		free_iova_mem(new_iova);
+		return IOVA_BAD_ADDR;
+	}
+	return new_iova->pfn_lo;
+}
+EXPORT_SYMBOL_GPL(alloc_iova_first_fit);
+
 /**
  * alloc_iova_fast - allocates an iova from rcache
  * @iovad: - iova domain in question
diff --git a/include/linux/iova.h b/include/linux/iova.h
index 46b5b10c532b..45ed6d41490a 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -89,6 +89,8 @@ void free_iova_fast(struct iova_domain *iovad, unsigned long pfn,
 		    unsigned long size);
 unsigned long alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
 			      unsigned long limit_pfn, bool flush_rcache);
+unsigned long alloc_iova_first_fit(struct iova_domain *iovad, unsigned long size,
+				   unsigned long limit_pfn);
 struct iova *reserve_iova(struct iova_domain *iovad, unsigned long pfn_lo,
 	unsigned long pfn_hi);
 void init_iova_domain(struct iova_domain *iovad, unsigned long granule,
-- 
2.17.1