drm/tegra: Add IOMMU support

When an IOMMU device is available on the platform bus, allocate an IOMMU
domain and attach the display controllers to it. The display controllers
can then scan out non-contiguous buffers by mapping them through the
IOMMU.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -9,6 +9,7 @@
 
 #include <linux/clk.h>
 #include <linux/debugfs.h>
+#include <linux/iommu.h>
 #include <linux/reset.h>
 
 #include <soc/tegra/pmc.h>
@@ -1290,6 +1291,17 @@ static int tegra_dc_init(struct host1x_client *client)
 	struct tegra_drm *tegra = drm->dev_private;
 	int err;
 
+	if (tegra->domain) {
+		err = iommu_attach_device(tegra->domain, dc->dev);
+		if (err < 0) {
+			dev_err(dc->dev, "failed to attach to domain: %d\n",
+				err);
+			return err;
+		}
+
+		dc->domain = tegra->domain;
+	}
+
 	drm_crtc_init(drm, &dc->base, &tegra_crtc_funcs);
 	drm_mode_crtc_set_gamma_size(&dc->base, 256);
 	drm_crtc_helper_add(&dc->base, &tegra_crtc_helper_funcs);
@@ -1347,6 +1359,11 @@ static int tegra_dc_exit(struct host1x_client *client)
 		return err;
 	}
 
+	if (dc->domain) {
+		iommu_detach_device(dc->domain, dc->dev);
+		dc->domain = NULL;
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/tegra/drm.c

@@ -8,6 +8,7 @@
  */
 
 #include <linux/host1x.h>
+#include <linux/iommu.h>
 
 #include "drm.h"
 #include "gem.h"
@@ -33,6 +34,17 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 	if (!tegra)
 		return -ENOMEM;
 
+	if (iommu_present(&platform_bus_type)) {
+		tegra->domain = iommu_domain_alloc(&platform_bus_type);
+		if (IS_ERR(tegra->domain)) {
+			err = PTR_ERR(tegra->domain);
+			goto free;
+		}
+
+		DRM_DEBUG("IOMMU context initialized\n");
+		drm_mm_init(&tegra->mm, 0, SZ_2G);
+	}
+
 	mutex_init(&tegra->clients_lock);
 	INIT_LIST_HEAD(&tegra->clients);
 	drm->dev_private = tegra;
@@ -76,6 +88,12 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 	tegra_drm_fb_free(drm);
 config:
 	drm_mode_config_cleanup(drm);
+
+	if (tegra->domain) {
+		iommu_domain_free(tegra->domain);
+		drm_mm_takedown(&tegra->mm);
+	}
+free:
 	kfree(tegra);
 	return err;
 }
@@ -83,6 +101,7 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
 static int tegra_drm_unload(struct drm_device *drm)
 {
 	struct host1x_device *device = to_host1x_device(drm->dev);
+	struct tegra_drm *tegra = drm->dev_private;
 	int err;
 
 	drm_kms_helper_poll_fini(drm);
@@ -94,6 +113,11 @@ static int tegra_drm_unload(struct drm_device *drm)
 	if (err < 0)
 		return err;
 
+	if (tegra->domain) {
+		iommu_domain_free(tegra->domain);
+		drm_mm_takedown(&tegra->mm);
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/tegra/drm.h

@@ -39,6 +39,9 @@ struct tegra_fbdev {
 struct tegra_drm {
 	struct drm_device *drm;
 
+	struct iommu_domain *domain;
+	struct drm_mm mm;
+
 	struct mutex clients_lock;
 	struct list_head clients;
 
@@ -121,6 +124,8 @@ struct tegra_dc {
 	struct drm_pending_vblank_event *event;
 
 	const struct tegra_dc_soc_info *soc;
+
+	struct iommu_domain *domain;
 };
 
 static inline struct tegra_dc *

drivers/gpu/drm/tegra/fb.c

@@ -65,9 +65,13 @@ static void tegra_fb_destroy(struct drm_framebuffer *framebuffer)
 	for (i = 0; i < fb->num_planes; i++) {
 		struct tegra_bo *bo = fb->planes[i];
 
-		if (bo)
+		if (bo) {
+			if (bo->pages && bo->vaddr)
+				vunmap(bo->vaddr);
+
 			drm_gem_object_unreference_unlocked(&bo->gem);
 		}
+	}
 
 	drm_framebuffer_cleanup(framebuffer);
 	kfree(fb->planes);
@@ -254,6 +258,16 @@ static int tegra_fbdev_probe(struct drm_fb_helper *helper,
 	offset = info->var.xoffset * bytes_per_pixel +
 		 info->var.yoffset * fb->pitches[0];
 
+	if (bo->pages) {
+		bo->vaddr = vmap(bo->pages, bo->num_pages, VM_MAP,
+				 pgprot_writecombine(PAGE_KERNEL));
+		if (!bo->vaddr) {
+			dev_err(drm->dev, "failed to vmap() framebuffer\n");
+			err = -ENOMEM;
+			goto destroy;
+		}
+	}
+
 	drm->mode_config.fb_base = (resource_size_t)bo->paddr;
 	info->screen_base = (void __iomem *)bo->vaddr + offset;
 	info->screen_size = size;

drivers/gpu/drm/tegra/gem.c

@@ -14,6 +14,7 @@
  */
 
 #include <linux/dma-buf.h>
+#include <linux/iommu.h>
 #include <drm/tegra_drm.h>
 
 #include "drm.h"
@@ -91,6 +92,88 @@ static const struct host1x_bo_ops tegra_bo_ops = {
 	.kunmap = tegra_bo_kunmap,
 };
 
+/*
+ * A generic iommu_map_sg() function is being reviewed and will hopefully be
+ * merged soon. At that point this function can be dropped in favour of the
+ * one provided by the IOMMU API.
+ */
+static ssize_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
+			      struct scatterlist *sg, unsigned int nents,
+			      int prot)
+{
+	struct scatterlist *s;
+	size_t offset = 0;
+	unsigned int i;
+	int err;
+
+	for_each_sg(sg, s, nents, i) {
+		phys_addr_t phys = page_to_phys(sg_page(s));
+		size_t length = s->offset + s->length;
+
+		err = iommu_map(domain, iova + offset, phys, length, prot);
+		if (err < 0) {
+			iommu_unmap(domain, iova, offset);
+			return err;
+		}
+
+		offset += length;
+	}
+
+	return offset;
+}
+
+static int tegra_bo_iommu_map(struct tegra_drm *tegra, struct tegra_bo *bo)
+{
+	int prot = IOMMU_READ | IOMMU_WRITE;
+	ssize_t err;
+
+	if (bo->mm)
+		return -EBUSY;
+
+	bo->mm = kzalloc(sizeof(*bo->mm), GFP_KERNEL);
+	if (!bo->mm)
+		return -ENOMEM;
+
+	err = drm_mm_insert_node_generic(&tegra->mm, bo->mm, bo->gem.size,
+					 PAGE_SIZE, 0, 0, 0);
+	if (err < 0) {
+		dev_err(tegra->drm->dev, "out of I/O virtual memory: %zd\n",
+			err);
+		goto free;
+	}
+
+	bo->paddr = bo->mm->start;
+
+	err = __iommu_map_sg(tegra->domain, bo->paddr, bo->sgt->sgl,
+			     bo->sgt->nents, prot);
+	if (err < 0) {
+		dev_err(tegra->drm->dev, "failed to map buffer: %zd\n", err);
+		goto remove;
+	}
+
+	bo->size = err;
+
+	return 0;
+
+remove:
+	drm_mm_remove_node(bo->mm);
+free:
+	kfree(bo->mm);
+	return err;
+}
+
+static int tegra_bo_iommu_unmap(struct tegra_drm *tegra, struct tegra_bo *bo)
+{
+	if (!bo->mm)
+		return 0;
+
+	iommu_unmap(tegra->domain, bo->paddr, bo->size);
+	drm_mm_remove_node(bo->mm);
+	kfree(bo->mm);
+
+	return 0;
+}
+
 static struct tegra_bo *tegra_bo_alloc_object(struct drm_device *drm,
 					      size_t size)
 {
@@ -121,9 +204,64 @@ static struct tegra_bo *tegra_bo_alloc_object(struct drm_device *drm,
 	return ERR_PTR(err);
 }
 
-static void tegra_bo_destroy(struct drm_device *drm, struct tegra_bo *bo)
+static void tegra_bo_free(struct drm_device *drm, struct tegra_bo *bo)
+{
+	if (bo->pages) {
+		drm_gem_put_pages(&bo->gem, bo->pages, true, true);
+		sg_free_table(bo->sgt);
+		kfree(bo->sgt);
+	} else {
+		dma_free_writecombine(drm->dev, bo->gem.size, bo->vaddr,
+				      bo->paddr);
+	}
+}
+
+static int tegra_bo_get_pages(struct drm_device *drm, struct tegra_bo *bo,
+			      size_t size)
 {
-	dma_free_writecombine(drm->dev, bo->gem.size, bo->vaddr, bo->paddr);
+	bo->pages = drm_gem_get_pages(&bo->gem);
+	if (IS_ERR(bo->pages))
+		return PTR_ERR(bo->pages);
+
+	bo->num_pages = size >> PAGE_SHIFT;
+
+	bo->sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages);
+	if (IS_ERR(bo->sgt)) {
+		drm_gem_put_pages(&bo->gem, bo->pages, false, false);
+		return PTR_ERR(bo->sgt);
+	}
+
+	return 0;
+}
+
+static int tegra_bo_alloc(struct drm_device *drm, struct tegra_bo *bo,
+			  size_t size)
+{
+	struct tegra_drm *tegra = drm->dev_private;
+	int err;
+
+	if (tegra->domain) {
+		err = tegra_bo_get_pages(drm, bo, size);
+		if (err < 0)
+			return err;
+
+		err = tegra_bo_iommu_map(tegra, bo);
+		if (err < 0) {
+			tegra_bo_free(drm, bo);
+			return err;
+		}
+	} else {
+		bo->vaddr = dma_alloc_writecombine(drm->dev, size, &bo->paddr,
+						   GFP_KERNEL | __GFP_NOWARN);
+		if (!bo->vaddr) {
+			dev_err(drm->dev,
+				"failed to allocate buffer of size %zu\n",
+				size);
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
 }
 
 struct tegra_bo *tegra_bo_create(struct drm_device *drm, unsigned int size,
@@ -136,14 +274,9 @@ struct tegra_bo *tegra_bo_create(struct drm_device *drm, unsigned int size,
 	if (IS_ERR(bo))
 		return bo;
 
-	bo->vaddr = dma_alloc_writecombine(drm->dev, size, &bo->paddr,
-					   GFP_KERNEL | __GFP_NOWARN);
-	if (!bo->vaddr) {
-		dev_err(drm->dev, "failed to allocate buffer with size %u\n",
-			size);
-		err = -ENOMEM;
-		goto err_dma;
-	}
+	err = tegra_bo_alloc(drm, bo, size);
+	if (err < 0)
+		goto release;
 
 	if (flags & DRM_TEGRA_GEM_CREATE_TILED)
 		bo->tiling.mode = TEGRA_BO_TILING_MODE_TILED;
@@ -153,9 +286,9 @@ struct tegra_bo *tegra_bo_create(struct drm_device *drm, unsigned int size,
 
 	return bo;
 
-err_dma:
+release:
+	drm_gem_object_release(&bo->gem);
 	kfree(bo);
-
 	return ERR_PTR(err);
 }
 
@@ -186,6 +319,7 @@ struct tegra_bo *tegra_bo_create_with_handle(struct drm_file *file,
 static struct tegra_bo *tegra_bo_import(struct drm_device *drm,
 					struct dma_buf *buf)
 {
+	struct tegra_drm *tegra = drm->dev_private;
 	struct dma_buf_attachment *attach;
 	struct tegra_bo *bo;
 	int err;
@@ -213,12 +347,19 @@ static struct tegra_bo *tegra_bo_import(struct drm_device *drm,
 		goto detach;
 	}
 
+	if (tegra->domain) {
+		err = tegra_bo_iommu_map(tegra, bo);
+		if (err < 0)
+			goto detach;
+	} else {
 		if (bo->sgt->nents > 1) {
 			err = -EINVAL;
 			goto detach;
 		}
 
 		bo->paddr = sg_dma_address(bo->sgt->sgl);
+	}
+
 	bo->gem.import_attach = attach;
 
 	return bo;
@@ -237,14 +378,18 @@ static struct tegra_bo *tegra_bo_import(struct drm_device *drm,
 
 void tegra_bo_free_object(struct drm_gem_object *gem)
 {
+	struct tegra_drm *tegra = gem->dev->dev_private;
 	struct tegra_bo *bo = to_tegra_bo(gem);
 
+	if (tegra->domain)
+		tegra_bo_iommu_unmap(tegra, bo);
+
 	if (gem->import_attach) {
 		dma_buf_unmap_attachment(gem->import_attach, bo->sgt,
 					 DMA_TO_DEVICE);
 		drm_prime_gem_destroy(gem, NULL);
 	} else {
-		tegra_bo_destroy(gem->dev, bo);
+		tegra_bo_free(gem->dev, bo);
 	}
 
 	drm_gem_object_release(gem);
@@ -299,14 +444,44 @@ int tegra_bo_dumb_map_offset(struct drm_file *file, struct drm_device *drm,
 	return 0;
 }
 
+static int tegra_bo_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct drm_gem_object *gem = vma->vm_private_data;
+	struct tegra_bo *bo = to_tegra_bo(gem);
+	struct page *page;
+	pgoff_t offset;
+	int err;
+
+	if (!bo->pages)
+		return VM_FAULT_SIGBUS;
+
+	offset = ((unsigned long)vmf->virtual_address - vma->vm_start) >> PAGE_SHIFT;
+	page = bo->pages[offset];
+
+	err = vm_insert_page(vma, (unsigned long)vmf->virtual_address, page);
+	switch (err) {
+	case -EAGAIN:
+	case 0:
+	case -ERESTARTSYS:
+	case -EINTR:
+	case -EBUSY:
+		return VM_FAULT_NOPAGE;
+
+	case -ENOMEM:
+		return VM_FAULT_OOM;
+	}
+
+	return VM_FAULT_SIGBUS;
+}
+
 const struct vm_operations_struct tegra_bo_vm_ops = {
+	.fault = tegra_bo_fault,
 	.open = drm_gem_vm_open,
 	.close = drm_gem_vm_close,
 };
 
 int tegra_drm_mmap(struct file *file, struct vm_area_struct *vma)
 {
-	unsigned long vm_pgoff = vma->vm_pgoff;
 	struct drm_gem_object *gem;
 	struct tegra_bo *bo;
 	int ret;
@@ -318,17 +493,28 @@ int tegra_drm_mmap(struct file *file, struct vm_area_struct *vma)
 	gem = vma->vm_private_data;
 	bo = to_tegra_bo(gem);
 
+	if (!bo->pages) {
+		unsigned long vm_pgoff = vma->vm_pgoff;
+
 		vma->vm_flags &= ~VM_PFNMAP;
 		vma->vm_pgoff = 0;
 
-	ret = dma_mmap_writecombine(gem->dev->dev, vma, bo->vaddr, bo->paddr,
-				    gem->size);
+		ret = dma_mmap_writecombine(gem->dev->dev, vma, bo->vaddr,
+					    bo->paddr, gem->size);
 		if (ret) {
 			drm_gem_vm_close(vma);
 			return ret;
 		}
 
 		vma->vm_pgoff = vm_pgoff;
+	} else {
+		pgprot_t prot = vm_get_page_prot(vma->vm_flags);
+
+		vma->vm_flags |= VM_MIXEDMAP;
+		vma->vm_flags &= ~VM_PFNMAP;
+
+		vma->vm_page_prot = pgprot_writecombine(prot);
+	}
 
 	return 0;
 }
@@ -345,21 +531,44 @@ tegra_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
 	if (!sgt)
 		return NULL;
 
-	if (sg_alloc_table(sgt, 1, GFP_KERNEL)) {
-		kfree(sgt);
-		return NULL;
-	}
+	if (bo->pages) {
+		struct scatterlist *sg;
+		unsigned int i;
+
+		if (sg_alloc_table(sgt, bo->num_pages, GFP_KERNEL))
+			goto free;
+
+		for_each_sg(sgt->sgl, sg, bo->num_pages, i)
+			sg_set_page(sg, bo->pages[i], PAGE_SIZE, 0);
+
+		if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0)
+			goto free;
+	} else {
+		if (sg_alloc_table(sgt, 1, GFP_KERNEL))
+			goto free;
 
 		sg_dma_address(sgt->sgl) = bo->paddr;
 		sg_dma_len(sgt->sgl) = gem->size;
+	}
 
 	return sgt;
+
+free:
+	sg_free_table(sgt);
+	kfree(sgt);
+	return NULL;
 }
 
 static void tegra_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,
 					  struct sg_table *sgt,
 					  enum dma_data_direction dir)
 {
+	struct drm_gem_object *gem = attach->dmabuf->priv;
+	struct tegra_bo *bo = to_tegra_bo(gem);
+
+	if (bo->pages)
+		dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+
 	sg_free_table(sgt);
 	kfree(sgt);
 }

drivers/gpu/drm/tegra/gem.h

@@ -38,6 +38,12 @@ struct tegra_bo {
 	dma_addr_t paddr;
 	void *vaddr;
 
+	struct drm_mm_node *mm;
+	unsigned long num_pages;
+	struct page **pages;
+	/* size of IOMMU mapping */
+	size_t size;
+
 	struct tegra_bo_tiling tiling;
 };