[PATCH v4 19/40] iommu: optimize subsystem by using atomic find_bit() API

[Yury Norov <yury.norov@gmail.com>]

Simplify __arm_smmu_alloc_bitmap() and msm_iommu_alloc_ctx() by using
a dedicated API, and make them nice one-liner wrappers.

While here, refactor msm_iommu_attach_dev() and msm_iommu_alloc_ctx()
so that error codes don't mismatch.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.h | 11 +++--------
 drivers/iommu/msm_iommu.c             | 19 +++++--------------
 2 files changed, 8 insertions(+), 22 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
index 4765c6945c34..c74d0300b64b 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
@@ -15,6 +15,7 @@
 #include <linux/bits.h>
 #include <linux/clk.h>
 #include <linux/device.h>
+#include <linux/find_atomic.h>
 #include <linux/io-64-nonatomic-hi-lo.h>
 #include <linux/io-pgtable.h>
 #include <linux/iommu.h>
@@ -455,15 +456,9 @@ struct arm_smmu_impl {
 
 static inline int __arm_smmu_alloc_bitmap(unsigned long *map, int start, int end)
 {
-	int idx;
+	int idx = find_and_set_next_bit(map, end, start);
 
-	do {
-		idx = find_next_zero_bit(map, end, start);
-		if (idx == end)
-			return -ENOSPC;
-	} while (test_and_set_bit(idx, map));
-
-	return idx;
+	return idx < end ? idx : -ENOSPC;
 }
 
 static inline void __iomem *arm_smmu_page(struct arm_smmu_device *smmu, int n)
diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 989e0869d805..4299e6a5b2ec 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -9,6 +9,7 @@
 #include <linux/init.h>
 #include <linux/platform_device.h>
 #include <linux/errno.h>
+#include <linux/find_atomic.h>
 #include <linux/io.h>
 #include <linux/io-pgtable.h>
 #include <linux/interrupt.h>
@@ -185,17 +186,9 @@ static const struct iommu_flush_ops msm_iommu_flush_ops = {
 	.tlb_add_page = __flush_iotlb_page,
 };
 
-static int msm_iommu_alloc_ctx(unsigned long *map, int start, int end)
+static int msm_iommu_alloc_ctx(struct msm_iommu_dev *iommu)
 {
-	int idx;
-
-	do {
-		idx = find_next_zero_bit(map, end, start);
-		if (idx == end)
-			return -ENOSPC;
-	} while (test_and_set_bit(idx, map));
-
-	return idx;
+	return find_and_set_bit(iommu->context_map, iommu->ncb);
 }
 
 static void msm_iommu_free_ctx(unsigned long *map, int idx)
@@ -418,10 +411,8 @@ static int msm_iommu_attach_dev(struct iommu_domain *domain, struct device *dev)
 					ret = -EEXIST;
 					goto fail;
 				}
-				master->num =
-					msm_iommu_alloc_ctx(iommu->context_map,
-							    0, iommu->ncb);
-				if (IS_ERR_VALUE(master->num)) {
+				master->num = msm_iommu_alloc_ctx(iommu);
+				if (master->num >= iommu->ncb) {
 					ret = -ENODEV;
 					goto fail;
 				}
-- 
2.43.0