x86: merge dma_supported

The code for both arches are very similar, so this patch merge them.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 44 insertions, 0 deletions

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 48cccbe51aa5..7d3bd652c36f 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -14,6 +14,8 @@ EXPORT_SYMBOL(forbid_dac);
 const struct dma_mapping_ops *dma_ops;
 EXPORT_SYMBOL(dma_ops);
 
+int iommu_sac_force __read_mostly = 0;
+
 #ifdef CONFIG_IOMMU_DEBUG
 int panic_on_overflow __read_mostly = 1;
 int force_iommu __read_mostly = 1;
@@ -103,6 +105,48 @@ void __init pci_iommu_alloc(void)
 }
 #endif
 
+int dma_supported(struct device *dev, u64 mask)
+{
+#ifdef CONFIG_PCI
+        if (mask > 0xffffffff && forbid_dac > 0) {
+                printk(KERN_INFO "PCI: Disallowing DAC for device %s\n",
+                                 dev->bus_id);
+                return 0;
+        }
+#endif
+
+        if (dma_ops->dma_supported)
+                return dma_ops->dma_supported(dev, mask);
+
+        /* Copied from i386. Doesn't make much sense, because it will
+           only work for pci_alloc_coherent.
+           The caller just has to use GFP_DMA in this case. */
+        if (mask < DMA_24BIT_MASK)
+                return 0;
+
+        /* Tell the device to use SAC when IOMMU force is on.  This
+           allows the driver to use cheaper accesses in some cases.
+
+           Problem with this is that if we overflow the IOMMU area and
+           return DAC as fallback address the device may not handle it
+           correctly.
+
+           As a special case some controllers have a 39bit address
+           mode that is as efficient as 32bit (aic79xx). Don't force
+           SAC for these.  Assume all masks <= 40 bits are of this
+           type. Normally this doesn't make any difference, but gives
+           more gentle handling of IOMMU overflow. */
+        if (iommu_sac_force && (mask >= DMA_40BIT_MASK)) {
+                printk(KERN_INFO "%s: Force SAC with mask %Lx\n",
+                                 dev->bus_id, mask);
+                return 0;
+        }
+
+        return 1;
+}
+EXPORT_SYMBOL(dma_supported);
+
+
 static int __init pci_iommu_init(void)
 {
 #ifdef CONFIG_CALGARY_IOMMU