diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 0e49a4560cff..e0af6cd7ba4f 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -190,7 +190,7 @@ static unsigned long iommu_range_alloc(struct device *dev,
 	unsigned int pool_nr;
 	struct iommu_pool *pool;
 
-	align_mask = 0xffffffffffffffffl >> (64 - align_order);
+	align_mask = (1ull << align_order) - 1;
 
 	/* This allocator was derived from x86_64's bit string search */