tile PCI RC: make default consistent DMA mask 32-bit

This change sets the PCI devices' initial DMA capabilities
conservatively and promotes them at the request of the driver,
as opposed to assuming advanced DMA capabilities. The old design
runs the risk of breaking drivers that assume default capabilities.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

2 files changed, 17 insertions, 9 deletions

diff --git a/arch/tile/include/asm/device.h b/arch/tile/include/asm/device.h
index 5182705bd05..6ab8bf146d4 100644
--- a/arch/tile/include/asm/device.h
+++ b/arch/tile/include/asm/device.h
@@ -23,7 +23,10 @@ struct dev_archdata {
 	/* Offset of the DMA address from the PA. */
 	dma_addr_t		dma_offset;
 
-	/* Highest DMA address that can be generated by this device. */
+	/*
+	 * Highest DMA address that can be generated by devices that
+	 * have limited DMA capability, i.e. non 64-bit capable.
+	 */
 	dma_addr_t		max_direct_dma_addr;
 };
 
diff --git a/arch/tile/include/asm/dma-mapping.h b/arch/tile/include/asm/dma-mapping.h
index 6f522d56913..1eae359d831 100644
--- a/arch/tile/include/asm/dma-mapping.h
+++ b/arch/tile/include/asm/dma-mapping.h
@@ -92,14 +92,19 @@ dma_set_mask(struct device *dev, u64 mask)
 {
 	struct dma_map_ops *dma_ops = get_dma_ops(dev);
 
-	/* Handle legacy PCI devices with limited memory addressability. */
-	if ((dma_ops == gx_pci_dma_map_ops ||
-	     dma_ops == gx_hybrid_pci_dma_map_ops ||
-	     dma_ops == gx_legacy_pci_dma_map_ops) &&
-	    (mask <= DMA_BIT_MASK(32))) {
-		set_dma_ops(dev, gx_legacy_pci_dma_map_ops);
-		set_dma_offset(dev, 0);
-		if (mask > dev->archdata.max_direct_dma_addr)
+	/*
+	 * For PCI devices with 64-bit DMA addressing capability, promote
+	 * the dma_ops to hybrid, with the consistent memory DMA space limited
+	 * to 32-bit. For 32-bit capable devices, limit the streaming DMA
+	 * address range to max_direct_dma_addr.
+	 */
+	if (dma_ops == gx_pci_dma_map_ops ||
+	    dma_ops == gx_hybrid_pci_dma_map_ops ||
+	    dma_ops == gx_legacy_pci_dma_map_ops) {
+		if (mask == DMA_BIT_MASK(64) &&
+		    dma_ops == gx_legacy_pci_dma_map_ops)
+			set_dma_ops(dev, gx_hybrid_pci_dma_map_ops);
+		else if (mask > dev->archdata.max_direct_dma_addr)
 			mask = dev->archdata.max_direct_dma_addr;
 	}