drm/tegra: Support kernel mappings with IOMMU

host1x command buffer patching requires that the buffer object can be
mapped into kernel address space. However, the recent addition of IOMMU
support did not account for this requirement. Therefore host1x engines
cannot be used if IOMMU is enabled.

This patch implements kmap, kunmap, mmap and munmap functions to host1x
buffer objects.
Signed-off-by: Arto Merilainen <amerilainen@nvidia.com>
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/gem.c

@@ -2,7 +2,7 @@
  * NVIDIA Tegra DRM GEM helper functions
  *
  * Copyright (C) 2012 Sascha Hauer, Pengutronix
- * Copyright (C) 2013 NVIDIA CORPORATION, All rights reserved.
+ * Copyright (C) 2013-2015 NVIDIA CORPORATION, All rights reserved.
  *
  * Based on the GEM/CMA helpers
  *
@@ -47,23 +47,51 @@ static void *tegra_bo_mmap(struct host1x_bo *bo)
 {
 	struct tegra_bo *obj = host1x_to_tegra_bo(bo);
 
-	return obj->vaddr;
+	if (obj->vaddr)
+		return obj->vaddr;
+	else if (obj->gem.import_attach)
+		return dma_buf_vmap(obj->gem.import_attach->dmabuf);
+	else
+		return vmap(obj->pages, obj->num_pages, VM_MAP,
+			    pgprot_writecombine(PAGE_KERNEL));
 }
 
 static void tegra_bo_munmap(struct host1x_bo *bo, void *addr)
 {
+	struct tegra_bo *obj = host1x_to_tegra_bo(bo);
+
+	if (obj->vaddr)
+		return;
+	else if (obj->gem.import_attach)
+		dma_buf_vunmap(obj->gem.import_attach->dmabuf, addr);
+	else
+		vunmap(addr);
 }
 
 static void *tegra_bo_kmap(struct host1x_bo *bo, unsigned int page)
 {
 	struct tegra_bo *obj = host1x_to_tegra_bo(bo);
 
-	return obj->vaddr + page * PAGE_SIZE;
+	if (obj->vaddr)
+		return obj->vaddr + page * PAGE_SIZE;
+	else if (obj->gem.import_attach)
+		return dma_buf_kmap(obj->gem.import_attach->dmabuf, page);
+	else
+		return vmap(obj->pages + page, 1, VM_MAP,
+			    pgprot_writecombine(PAGE_KERNEL));
 }
 
 static void tegra_bo_kunmap(struct host1x_bo *bo, unsigned int page,
 			    void *addr)
 {
+	struct tegra_bo *obj = host1x_to_tegra_bo(bo);
+
+	if (obj->vaddr)
+		return;
+	else if (obj->gem.import_attach)
+		dma_buf_kunmap(obj->gem.import_attach->dmabuf, page, addr);
+	else
+		vunmap(addr);
 }
 
 static struct host1x_bo *tegra_bo_get(struct host1x_bo *bo)