diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index ff5a6ce027b8..8226c6cb348a 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -215,7 +215,8 @@ static unsigned long iommu_range_alloc(struct device *dev,
 	spin_lock_irqsave(&(pool->lock), flags);
 
 again:
-	if ((pass == 0) && handle && *handle)
+	if ((pass == 0) && handle && *handle &&
+	    (*handle >= pool->start) && (*handle < pool->end))
 		start = *handle;
 	else
 		start = pool->hint;
@@ -236,7 +237,9 @@ again:
 		 * but on second pass, start at 0 in pool 0.
 		 */
 		if ((start & mask) >= limit || pass > 0) {
+			spin_unlock(&(pool->lock));
 			pool = &(tbl->pools[0]);
+			spin_lock(&(pool->lock));
 			start = pool->start;
 		} else {
 			start &= mask;
diff --git a/arch/powerpc/sysdev/dart_iommu.c b/arch/powerpc/sysdev/dart_iommu.c
index 8ef63a01e345..bd968a43a48b 100644
--- a/arch/powerpc/sysdev/dart_iommu.c
+++ b/arch/powerpc/sysdev/dart_iommu.c
@@ -73,11 +73,16 @@ static int dart_is_u4;
 
 #define DBG(...)
 
+static DEFINE_SPINLOCK(invalidate_lock);
+
 static inline void dart_tlb_invalidate_all(void)
 {
 	unsigned long l = 0;
 	unsigned int reg, inv_bit;
 	unsigned long limit;
+	unsigned long flags;
+
+	spin_lock_irqsave(&invalidate_lock, flags);
 
 	DBG("dart: flush\n");
 
@@ -110,12 +115,17 @@ retry:
 			panic("DART: TLB did not flush after waiting a long "
 			      "time. Buggy U3 ?");
 	}
+
+	spin_unlock_irqrestore(&invalidate_lock, flags);
 }
 
 static inline void dart_tlb_invalidate_one(unsigned long bus_rpn)
 {
 	unsigned int reg;
 	unsigned int l, limit;
+	unsigned long flags;
+
+	spin_lock_irqsave(&invalidate_lock, flags);
 
 	reg = DART_CNTL_U4_ENABLE | DART_CNTL_U4_IONE |
 		(bus_rpn & DART_CNTL_U4_IONE_MASK);
@@ -137,6 +147,8 @@ wait_more:
 			panic("DART: TLB did not flush after waiting a long "
 			      "time. Buggy U4 ?");
 	}
+
+	spin_unlock_irqrestore(&invalidate_lock, flags);
 }
 
 static void dart_flush(struct iommu_table *tbl)