drm/nouveau/ttm: set the DMA mask for platform devices

So far the DMA mask was not set for platform devices, which limited them
to a 32-bit physical space. Allow dma_set_mask() to be called for
non-PCI devices, and also take the IOMMU bit into account since it could
restrict the physically addressable space.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_ttm.c

@@ -29,6 +29,9 @@
 #include "nouveau_gem.h"
 
 #include "drm_legacy.h"
+
+#include <core/tegra.h>
+
 static int
 nouveau_vram_manager_init(struct ttm_mem_type_manager *man, unsigned long psize)
 {
@@ -353,16 +356,26 @@ nouveau_ttm_init(struct nouveau_drm *drm)
 		if (drm->agp.bridge ||
 		     !dma_supported(dev->dev, DMA_BIT_MASK(bits)))
 			bits = 32;
+	} else if (device->func->tegra) {
+		struct nvkm_device_tegra *tegra = device->func->tegra(device);
 
-		ret = dma_set_mask(dev->dev, DMA_BIT_MASK(bits));
-		if (ret)
-			return ret;
+		/*
+		 * If the platform can use a IOMMU, then the addressable DMA
+		 * space is constrained by the IOMMU bit
+		 */
+		if (tegra->func->iommu_bit)
+			bits = min(bits, tegra->func->iommu_bit);
 
-		ret = dma_set_coherent_mask(dev->dev, DMA_BIT_MASK(bits));
-		if (ret)
-			dma_set_coherent_mask(dev->dev, DMA_BIT_MASK(32));
 	}
 
+	ret = dma_set_mask(dev->dev, DMA_BIT_MASK(bits));
+	if (ret)
+		return ret;
+
+	ret = dma_set_coherent_mask(dev->dev, DMA_BIT_MASK(bits));
+	if (ret)
+		dma_set_coherent_mask(dev->dev, DMA_BIT_MASK(32));
+
 	ret = nouveau_ttm_global_init(drm);
 	if (ret)
 		return ret;