sparc64/pci_sun4v: fix ATU checks for large DMA masks

Now that we allow drivers to always need to set larger than required
DMA masks we need to be a little more careful in the sun4v PCI iommu
driver to chose when to select the ATU support - a larger DMA mask
can be set even when the platform does not support ATU, so we always
have to check if it is avaiable before using it.  Add a little helper
for that and use it in all the places where we make ATU usage decisions
based on the DMA mask.

Fixes: 24132a419c ("sparc64/pci_sun4v: allow large DMA masks")
Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Meelis Roos <mroos@linux.ee>
Acked-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/pci_sun4v.c

@@ -73,6 +73,11 @@ static inline void iommu_batch_start(struct device *dev, unsigned long prot, uns
 	p->npages	= 0;
 }
 
+static inline bool iommu_use_atu(struct iommu *iommu, u64 mask)
+{
+	return iommu->atu && mask > DMA_BIT_MASK(32);
+}
+
 /* Interrupts must be disabled.  */
 static long iommu_batch_flush(struct iommu_batch *p, u64 mask)
 {
@@ -92,7 +97,7 @@ static long iommu_batch_flush(struct iommu_batch *p, u64 mask)
 		prot &= (HV_PCI_MAP_ATTR_READ | HV_PCI_MAP_ATTR_WRITE);
 
 	while (npages != 0) {
-		if (mask <= DMA_BIT_MASK(32) || !pbm->iommu->atu) {
+		if (!iommu_use_atu(pbm->iommu, mask)) {
 			num = pci_sun4v_iommu_map(devhandle,
 						  HV_PCI_TSBID(0, entry),
 						  npages,
@@ -179,7 +184,6 @@ static void *dma_4v_alloc_coherent(struct device *dev, size_t size,
 	unsigned long flags, order, first_page, npages, n;
 	unsigned long prot = 0;
 	struct iommu *iommu;
-	struct atu *atu;
 	struct iommu_map_table *tbl;
 	struct page *page;
 	void *ret;
@@ -205,13 +209,11 @@ static void *dma_4v_alloc_coherent(struct device *dev, size_t size,
 	memset((char *)first_page, 0, PAGE_SIZE << order);
 
 	iommu = dev->archdata.iommu;
-	atu = iommu->atu;
-
 	mask = dev->coherent_dma_mask;
-	if (mask <= DMA_BIT_MASK(32) || !atu)
+	if (!iommu_use_atu(iommu, mask))
 		tbl = &iommu->tbl;
 	else
-		tbl = &atu->tbl;
+		tbl = &iommu->atu->tbl;
 
 	entry = iommu_tbl_range_alloc(dev, tbl, npages, NULL,
 				      (unsigned long)(-1), 0);
@@ -333,7 +335,7 @@ static void dma_4v_free_coherent(struct device *dev, size_t size, void *cpu,
 	atu = iommu->atu;
 	devhandle = pbm->devhandle;
 
-	if (dvma <= DMA_BIT_MASK(32)) {
+	if (!iommu_use_atu(iommu, dvma)) {
 		tbl = &iommu->tbl;
 		iotsb_num = 0; /* we don't care for legacy iommu */
 	} else {
@@ -374,7 +376,7 @@ static dma_addr_t dma_4v_map_page(struct device *dev, struct page *page,
 	npages >>= IO_PAGE_SHIFT;
 
 	mask = *dev->dma_mask;
-	if (mask <= DMA_BIT_MASK(32))
+	if (!iommu_use_atu(iommu, mask))
 		tbl = &iommu->tbl;
 	else
 		tbl = &atu->tbl;
@@ -510,7 +512,7 @@ static int dma_4v_map_sg(struct device *dev, struct scatterlist *sglist,
 				  IO_PAGE_SIZE) >> IO_PAGE_SHIFT;
 
 	mask = *dev->dma_mask;
-	if (mask <= DMA_BIT_MASK(32))
+	if (!iommu_use_atu(iommu, mask))
 		tbl = &iommu->tbl;
 	else
 		tbl = &atu->tbl;