drm/tegra: Add PRIME support

Implement very basic PRIME support. This currently only works with
buffers that are contiguous in memory and will refuse to import any
physically non-contiguous buffers.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/drm.c

@@ -580,7 +580,7 @@ static void tegra_debugfs_cleanup(struct drm_minor *minor)
 #endif
 
 static struct drm_driver tegra_drm_driver = {
-	.driver_features = DRIVER_MODESET | DRIVER_GEM,
+	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_PRIME,
 	.load = tegra_drm_load,
 	.unload = tegra_drm_unload,
 	.open = tegra_drm_open,
@@ -598,6 +598,12 @@ static struct drm_driver tegra_drm_driver = {
 
 	.gem_free_object = tegra_bo_free_object,
 	.gem_vm_ops = &tegra_bo_vm_ops,
+
+	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
+	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
+	.gem_prime_export = tegra_gem_prime_export,
+	.gem_prime_import = tegra_gem_prime_import,
+
 	.dumb_create = tegra_bo_dumb_create,
 	.dumb_map_offset = tegra_bo_dumb_map_offset,
 	.dumb_destroy = drm_gem_dumb_destroy,

drivers/gpu/drm/tegra/gem.c

@@ -18,6 +18,7 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/dma-buf.h>
 #include <drm/tegra_drm.h>
 
 #include "gem.h"
@@ -173,13 +174,87 @@ struct tegra_bo *tegra_bo_create_with_handle(struct drm_file *file,
 	return ERR_PTR(ret);
 }
 
+struct tegra_bo *tegra_bo_import(struct drm_device *drm, struct dma_buf *buf)
+{
+	struct dma_buf_attachment *attach;
+	struct tegra_bo *bo;
+	ssize_t size;
+	int err;
+
+	bo = kzalloc(sizeof(*bo), GFP_KERNEL);
+	if (!bo)
+		return ERR_PTR(-ENOMEM);
+
+	host1x_bo_init(&bo->base, &tegra_bo_ops);
+	size = round_up(buf->size, PAGE_SIZE);
+
+	err = drm_gem_object_init(drm, &bo->gem, size);
+	if (err < 0)
+		goto free;
+
+	err = drm_gem_create_mmap_offset(&bo->gem);
+	if (err < 0)
+		goto release;
+
+	attach = dma_buf_attach(buf, drm->dev);
+	if (IS_ERR(attach)) {
+		err = PTR_ERR(attach);
+		goto free_mmap;
+	}
+
+	get_dma_buf(buf);
+
+	bo->sgt = dma_buf_map_attachment(attach, DMA_TO_DEVICE);
+	if (!bo->sgt) {
+		err = -ENOMEM;
+		goto detach;
+	}
+
+	if (IS_ERR(bo->sgt)) {
+		err = PTR_ERR(bo->sgt);
+		goto detach;
+	}
+
+	if (bo->sgt->nents > 1) {
+		err = -EINVAL;
+		goto detach;
+	}
+
+	bo->paddr = sg_dma_address(bo->sgt->sgl);
+	bo->gem.import_attach = attach;
+
+	return bo;
+
+detach:
+	if (!IS_ERR_OR_NULL(bo->sgt))
+		dma_buf_unmap_attachment(attach, bo->sgt, DMA_TO_DEVICE);
+
+	dma_buf_detach(buf, attach);
+	dma_buf_put(buf);
+free_mmap:
+	drm_gem_free_mmap_offset(&bo->gem);
+release:
+	drm_gem_object_release(&bo->gem);
+free:
+	kfree(bo);
+
+	return ERR_PTR(err);
+}
+
 void tegra_bo_free_object(struct drm_gem_object *gem)
 {
 	struct tegra_bo *bo = to_tegra_bo(gem);
 
+	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);
+	}
+
 	drm_gem_free_mmap_offset(gem);
 	drm_gem_object_release(gem);
-	tegra_bo_destroy(gem->dev, bo);
 
 	kfree(bo);
 }
@@ -255,3 +330,106 @@ int tegra_drm_mmap(struct file *file, struct vm_area_struct *vma)
 
 	return ret;
 }
+
+static struct sg_table *
+tegra_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
+			    enum dma_data_direction dir)
+{
+	struct drm_gem_object *gem = attach->dmabuf->priv;
+	struct tegra_bo *bo = to_tegra_bo(gem);
+	struct sg_table *sgt;
+
+	sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
+	if (!sgt)
+		return NULL;
+
+	if (sg_alloc_table(sgt, 1, GFP_KERNEL)) {
+		kfree(sgt);
+		return NULL;
+	}
+
+	sg_dma_address(sgt->sgl) = bo->paddr;
+	sg_dma_len(sgt->sgl) = gem->size;
+
+	return sgt;
+}
+
+static void tegra_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,
+					  struct sg_table *sgt,
+					  enum dma_data_direction dir)
+{
+	sg_free_table(sgt);
+	kfree(sgt);
+}
+
+static void tegra_gem_prime_release(struct dma_buf *buf)
+{
+	drm_gem_dmabuf_release(buf);
+}
+
+static void *tegra_gem_prime_kmap_atomic(struct dma_buf *buf,
+					 unsigned long page)
+{
+	return NULL;
+}
+
+static void tegra_gem_prime_kunmap_atomic(struct dma_buf *buf,
+					  unsigned long page,
+					  void *addr)
+{
+}
+
+static void *tegra_gem_prime_kmap(struct dma_buf *buf, unsigned long page)
+{
+	return NULL;
+}
+
+static void tegra_gem_prime_kunmap(struct dma_buf *buf, unsigned long page,
+				   void *addr)
+{
+}
+
+static int tegra_gem_prime_mmap(struct dma_buf *buf, struct vm_area_struct *vma)
+{
+	return -EINVAL;
+}
+
+static const struct dma_buf_ops tegra_gem_prime_dmabuf_ops = {
+	.map_dma_buf = tegra_gem_prime_map_dma_buf,
+	.unmap_dma_buf = tegra_gem_prime_unmap_dma_buf,
+	.release = tegra_gem_prime_release,
+	.kmap_atomic = tegra_gem_prime_kmap_atomic,
+	.kunmap_atomic = tegra_gem_prime_kunmap_atomic,
+	.kmap = tegra_gem_prime_kmap,
+	.kunmap = tegra_gem_prime_kunmap,
+	.mmap = tegra_gem_prime_mmap,
+};
+
+struct dma_buf *tegra_gem_prime_export(struct drm_device *drm,
+				       struct drm_gem_object *gem,
+				       int flags)
+{
+	return dma_buf_export(gem, &tegra_gem_prime_dmabuf_ops, gem->size,
+			      flags);
+}
+
+struct drm_gem_object *tegra_gem_prime_import(struct drm_device *drm,
+					      struct dma_buf *buf)
+{
+	struct tegra_bo *bo;
+
+	if (buf->ops == &tegra_gem_prime_dmabuf_ops) {
+		struct drm_gem_object *gem = buf->priv;
+
+		if (gem->dev == drm) {
+			drm_gem_object_reference(gem);
+			return gem;
+		}
+	}
+
+	bo = tegra_bo_import(drm, buf);
+	if (IS_ERR(bo))
+		return ERR_CAST(bo);
+
+	return &bo->gem;
+}

drivers/gpu/drm/tegra/gem.h

@@ -31,6 +31,7 @@ struct tegra_bo {
 	struct drm_gem_object gem;
 	struct host1x_bo base;
 	unsigned long flags;
+	struct sg_table *sgt;
 	dma_addr_t paddr;
 	void *vaddr;
 };
@@ -57,4 +58,10 @@ int tegra_drm_mmap(struct file *file, struct vm_area_struct *vma);
 
 extern const struct vm_operations_struct tegra_bo_vm_ops;
 
+struct dma_buf *tegra_gem_prime_export(struct drm_device *drm,
+				       struct drm_gem_object *gem,
+				       int flags);
+struct drm_gem_object *tegra_gem_prime_import(struct drm_device *drm,
+					      struct dma_buf *buf);
+
 #endif