Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 776 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
new file mode 100644
index 000000000..e435f986c
--- /dev/null
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -0,0 +1,776 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018 Noralf Trønnes
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/shmem_fs.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/module.h>
+
+#ifdef CONFIG_X86
+#include <asm/set_memory.h>
+#endif
+
+#include <drm/drm.h>
+#include <drm/drm_device.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_prime.h>
+#include <drm/drm_print.h>
+
+MODULE_IMPORT_NS(DMA_BUF);
+
+/**
+ * DOC: overview
+ *
+ * This library provides helpers for GEM objects backed by shmem buffers
+ * allocated using anonymous pageable memory.
+ *
+ * Functions that operate on the GEM object receive struct &drm_gem_shmem_object.
+ * For GEM callback helpers in struct &drm_gem_object functions, see likewise
+ * named functions with an _object_ infix (e.g., drm_gem_shmem_object_vmap() wraps
+ * drm_gem_shmem_vmap()). These helpers perform the necessary type conversion.
+ */
+
+static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
+	.free = drm_gem_shmem_object_free,
+	.print_info = drm_gem_shmem_object_print_info,
+	.pin = drm_gem_shmem_object_pin,
+	.unpin = drm_gem_shmem_object_unpin,
+	.get_sg_table = drm_gem_shmem_object_get_sg_table,
+	.vmap = drm_gem_shmem_object_vmap,
+	.vunmap = drm_gem_shmem_object_vunmap,
+	.mmap = drm_gem_shmem_object_mmap,
+	.vm_ops = &drm_gem_shmem_vm_ops,
+};
+
+static struct drm_gem_shmem_object *
+__drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
+{
+	struct drm_gem_shmem_object *shmem;
+	struct drm_gem_object *obj;
+	int ret = 0;
+
+	size = PAGE_ALIGN(size);
+
+	if (dev->driver->gem_create_object) {
+		obj = dev->driver->gem_create_object(dev, size);
+		if (IS_ERR(obj))
+			return ERR_CAST(obj);
+		shmem = to_drm_gem_shmem_obj(obj);
+	} else {
+		shmem = kzalloc(sizeof(*shmem), GFP_KERNEL);
+		if (!shmem)
+			return ERR_PTR(-ENOMEM);
+		obj = &shmem->base;
+	}
+
+	if (!obj->funcs)
+		obj->funcs = &drm_gem_shmem_funcs;
+
+	if (private) {
+		drm_gem_private_object_init(dev, obj, size);
+		shmem->map_wc = false; /* dma-buf mappings use always writecombine */
+	} else {
+		ret = drm_gem_object_init(dev, obj, size);
+	}
+	if (ret) {
+		drm_gem_private_object_fini(obj);
+		goto err_free;
+	}
+
+	ret = drm_gem_create_mmap_offset(obj);
+	if (ret)
+		goto err_release;
+
+	INIT_LIST_HEAD(&shmem->madv_list);
+
+	if (!private) {
+		/*
+		 * Our buffers are kept pinned, so allocating them
+		 * from the MOVABLE zone is a really bad idea, and
+		 * conflicts with CMA. See comments above new_inode()
+		 * why this is required _and_ expected if you're
+		 * going to pin these pages.
+		 */
+		mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER |
+				     __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
+	}
+
+	return shmem;
+
+err_release:
+	drm_gem_object_release(obj);
+err_free:
+	kfree(obj);
+
+	return ERR_PTR(ret);
+}
+/**
+ * drm_gem_shmem_create - Allocate an object with the given size
+ * @dev: DRM device
+ * @size: Size of the object to allocate
+ *
+ * This function creates a shmem GEM object.
+ *
+ * Returns:
+ * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
+{
+	return __drm_gem_shmem_create(dev, size, false);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
+
+/**
+ * drm_gem_shmem_free - Free resources associated with a shmem GEM object
+ * @shmem: shmem GEM object to free
+ *
+ * This function cleans up the GEM object state and frees the memory used to
+ * store the object itself.
+ */
+void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	if (obj->import_attach) {
+		drm_prime_gem_destroy(obj, shmem->sgt);
+	} else {
+		dma_resv_lock(shmem->base.resv, NULL);
+
+		drm_WARN_ON(obj->dev, shmem->vmap_use_count);
+
+		if (shmem->sgt) {
+			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
+					  DMA_BIDIRECTIONAL, 0);
+			sg_free_table(shmem->sgt);
+			kfree(shmem->sgt);
+		}
+		if (shmem->pages)
+			drm_gem_shmem_put_pages(shmem);
+
+		drm_WARN_ON(obj->dev, shmem->pages_use_count);
+
+		dma_resv_unlock(shmem->base.resv);
+	}
+
+	drm_gem_object_release(obj);
+	kfree(shmem);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
+
+static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct page **pages;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (shmem->pages_use_count++ > 0)
+		return 0;
+
+	pages = drm_gem_get_pages(obj);
+	if (IS_ERR(pages)) {
+		drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n",
+			    PTR_ERR(pages));
+		shmem->pages_use_count = 0;
+		return PTR_ERR(pages);
+	}
+
+	/*
+	 * TODO: Allocating WC pages which are correctly flushed is only
+	 * supported on x86. Ideal solution would be a GFP_WC flag, which also
+	 * ttm_pool.c could use.
+	 */
+#ifdef CONFIG_X86
+	if (shmem->map_wc)
+		set_pages_array_wc(pages, obj->size >> PAGE_SHIFT);
+#endif
+
+	shmem->pages = pages;
+
+	return 0;
+}
+
+/*
+ * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function decreases the use count and puts the backing pages when use drops to zero.
+ */
+void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
+		return;
+
+	if (--shmem->pages_use_count > 0)
+		return;
+
+#ifdef CONFIG_X86
+	if (shmem->map_wc)
+		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
+#endif
+
+	drm_gem_put_pages(obj, shmem->pages,
+			  shmem->pages_mark_dirty_on_put,
+			  shmem->pages_mark_accessed_on_put);
+	shmem->pages = NULL;
+}
+EXPORT_SYMBOL(drm_gem_shmem_put_pages);
+
+static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	ret = drm_gem_shmem_get_pages(shmem);
+
+	return ret;
+}
+
+static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
+{
+	dma_resv_assert_held(shmem->base.resv);
+
+	drm_gem_shmem_put_pages(shmem);
+}
+
+/**
+ * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function makes sure the backing pages are pinned in memory while the
+ * buffer is exported.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	int ret;
+
+	drm_WARN_ON(obj->dev, obj->import_attach);
+
+	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
+	if (ret)
+		return ret;
+	ret = drm_gem_shmem_pin_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_gem_shmem_pin);
+
+/**
+ * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function removes the requirement that the backing pages are pinned in
+ * memory.
+ */
+void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	drm_WARN_ON(obj->dev, obj->import_attach);
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	drm_gem_shmem_unpin_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+}
+EXPORT_SYMBOL(drm_gem_shmem_unpin);
+
+/*
+ * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
+ * @shmem: shmem GEM object
+ * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
+ *       store.
+ *
+ * This function makes sure that a contiguous kernel virtual address mapping
+ * exists for the buffer backing the shmem GEM object. It hides the differences
+ * between dma-buf imported and natively allocated objects.
+ *
+ * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap().
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
+		       struct iosys_map *map)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	int ret = 0;
+
+	if (obj->import_attach) {
+		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
+		if (!ret) {
+			if (drm_WARN_ON(obj->dev, map->is_iomem)) {
+				dma_buf_vunmap(obj->import_attach->dmabuf, map);
+				return -EIO;
+			}
+		}
+	} else {
+		pgprot_t prot = PAGE_KERNEL;
+
+		dma_resv_assert_held(shmem->base.resv);
+
+		if (shmem->vmap_use_count++ > 0) {
+			iosys_map_set_vaddr(map, shmem->vaddr);
+			return 0;
+		}
+
+		ret = drm_gem_shmem_get_pages(shmem);
+		if (ret)
+			goto err_zero_use;
+
+		if (shmem->map_wc)
+			prot = pgprot_writecombine(prot);
+		shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
+				    VM_MAP, prot);
+		if (!shmem->vaddr)
+			ret = -ENOMEM;
+		else
+			iosys_map_set_vaddr(map, shmem->vaddr);
+	}
+
+	if (ret) {
+		drm_dbg_kms(obj->dev, "Failed to vmap pages, error %d\n", ret);
+		goto err_put_pages;
+	}
+
+	return 0;
+
+err_put_pages:
+	if (!obj->import_attach)
+		drm_gem_shmem_put_pages(shmem);
+err_zero_use:
+	shmem->vmap_use_count = 0;
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_gem_shmem_vmap);
+
+/*
+ * drm_gem_shmem_vunmap - Unmap a virtual mapping for a shmem GEM object
+ * @shmem: shmem GEM object
+ * @map: Kernel virtual address where the SHMEM GEM object was mapped
+ *
+ * This function cleans up a kernel virtual address mapping acquired by
+ * drm_gem_shmem_vmap(). The mapping is only removed when the use count drops to
+ * zero.
+ *
+ * This function hides the differences between dma-buf imported and natively
+ * allocated objects.
+ */
+void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
+			  struct iosys_map *map)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	if (obj->import_attach) {
+		dma_buf_vunmap(obj->import_attach->dmabuf, map);
+	} else {
+		dma_resv_assert_held(shmem->base.resv);
+
+		if (drm_WARN_ON_ONCE(obj->dev, !shmem->vmap_use_count))
+			return;
+
+		if (--shmem->vmap_use_count > 0)
+			return;
+
+		vunmap(shmem->vaddr);
+		drm_gem_shmem_put_pages(shmem);
+	}
+
+	shmem->vaddr = NULL;
+}
+EXPORT_SYMBOL(drm_gem_shmem_vunmap);
+
+static int
+drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
+				 struct drm_device *dev, size_t size,
+				 uint32_t *handle)
+{
+	struct drm_gem_shmem_object *shmem;
+	int ret;
+
+	shmem = drm_gem_shmem_create(dev, size);
+	if (IS_ERR(shmem))
+		return PTR_ERR(shmem);
+
+	/*
+	 * Allocate an id of idr table where the obj is registered
+	 * and handle has the id what user can see.
+	 */
+	ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
+	/* drop reference from allocate - handle holds it now. */
+	drm_gem_object_put(&shmem->base);
+
+	return ret;
+}
+
+/* Update madvise status, returns true if not purged, else
+ * false or -errno.
+ */
+int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
+{
+	dma_resv_assert_held(shmem->base.resv);
+
+	if (shmem->madv >= 0)
+		shmem->madv = madv;
+
+	madv = shmem->madv;
+
+	return (madv >= 0);
+}
+EXPORT_SYMBOL(drm_gem_shmem_madvise);
+
+void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	struct drm_device *dev = obj->dev;
+
+	dma_resv_assert_held(shmem->base.resv);
+
+	drm_WARN_ON(obj->dev, !drm_gem_shmem_is_purgeable(shmem));
+
+	dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
+	sg_free_table(shmem->sgt);
+	kfree(shmem->sgt);
+	shmem->sgt = NULL;
+
+	drm_gem_shmem_put_pages(shmem);
+
+	shmem->madv = -1;
+
+	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
+	drm_gem_free_mmap_offset(obj);
+
+	/* Our goal here is to return as much of the memory as
+	 * is possible back to the system as we are called from OOM.
+	 * To do this we must instruct the shmfs to drop all of its
+	 * backing pages, *now*.
+	 */
+	shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
+
+	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
+}
+EXPORT_SYMBOL(drm_gem_shmem_purge);
+
+/**
+ * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
+ * @file: DRM file structure to create the dumb buffer for
+ * @dev: DRM device
+ * @args: IOCTL data
+ *
+ * This function computes the pitch of the dumb buffer and rounds it up to an
+ * integer number of bytes per pixel. Drivers for hardware that doesn't have
+ * any additional restrictions on the pitch can directly use this function as
+ * their &drm_driver.dumb_create callback.
+ *
+ * For hardware with additional restrictions, drivers can adjust the fields
+ * set up by userspace before calling into this function.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
+			      struct drm_mode_create_dumb *args)
+{
+	u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
+
+	if (!args->pitch || !args->size) {
+		args->pitch = min_pitch;
+		args->size = PAGE_ALIGN(args->pitch * args->height);
+	} else {
+		/* ensure sane minimum values */
+		if (args->pitch < min_pitch)
+			args->pitch = min_pitch;
+		if (args->size < args->pitch * args->height)
+			args->size = PAGE_ALIGN(args->pitch * args->height);
+	}
+
+	return drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
+
+static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct drm_gem_object *obj = vma->vm_private_data;
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+	loff_t num_pages = obj->size >> PAGE_SHIFT;
+	vm_fault_t ret;
+	struct page *page;
+	pgoff_t page_offset;
+
+	/* We don't use vmf->pgoff since that has the fake offset */
+	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
+
+	dma_resv_lock(shmem->base.resv, NULL);
+
+	if (page_offset >= num_pages ||
+	    drm_WARN_ON_ONCE(obj->dev, !shmem->pages) ||
+	    shmem->madv < 0) {
+		ret = VM_FAULT_SIGBUS;
+	} else {
+		page = shmem->pages[page_offset];
+
+		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
+	}
+
+	dma_resv_unlock(shmem->base.resv);
+
+	return ret;
+}
+
+static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj = vma->vm_private_data;
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+
+	drm_WARN_ON(obj->dev, obj->import_attach);
+
+	dma_resv_lock(shmem->base.resv, NULL);
+
+	/*
+	 * We should have already pinned the pages when the buffer was first
+	 * mmap'd, vm_open() just grabs an additional reference for the new
+	 * mm the vma is getting copied into (ie. on fork()).
+	 */
+	if (!drm_WARN_ON_ONCE(obj->dev, !shmem->pages_use_count))
+		shmem->pages_use_count++;
+
+	dma_resv_unlock(shmem->base.resv);
+
+	drm_gem_vm_open(vma);
+}
+
+static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj = vma->vm_private_data;
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	drm_gem_shmem_put_pages(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	drm_gem_vm_close(vma);
+}
+
+const struct vm_operations_struct drm_gem_shmem_vm_ops = {
+	.fault = drm_gem_shmem_fault,
+	.open = drm_gem_shmem_vm_open,
+	.close = drm_gem_shmem_vm_close,
+};
+EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);
+
+/**
+ * drm_gem_shmem_mmap - Memory-map a shmem GEM object
+ * @shmem: shmem GEM object
+ * @vma: VMA for the area to be mapped
+ *
+ * This function implements an augmented version of the GEM DRM file mmap
+ * operation for shmem objects.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	int ret;
+
+	if (obj->import_attach) {
+		/* Reset both vm_ops and vm_private_data, so we don't end up with
+		 * vm_ops pointing to our implementation if the dma-buf backend
+		 * doesn't set those fields.
+		 */
+		vma->vm_private_data = NULL;
+		vma->vm_ops = NULL;
+
+		ret = dma_buf_mmap(obj->dma_buf, vma, 0);
+
+		/* Drop the reference drm_gem_mmap_obj() acquired.*/
+		if (!ret)
+			drm_gem_object_put(obj);
+
+		return ret;
+	}
+
+	dma_resv_lock(shmem->base.resv, NULL);
+	ret = drm_gem_shmem_get_pages(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	if (ret)
+		return ret;
+
+	vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
+	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+	if (shmem->map_wc)
+		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
+
+/**
+ * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
+ * @shmem: shmem GEM object
+ * @p: DRM printer
+ * @indent: Tab indentation level
+ */
+void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
+			      struct drm_printer *p, unsigned int indent)
+{
+	if (shmem->base.import_attach)
+		return;
+
+	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
+	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
+	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
+}
+EXPORT_SYMBOL(drm_gem_shmem_print_info);
+
+/**
+ * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
+ *                              pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function exports a scatter/gather table suitable for PRIME usage by
+ * calling the standard DMA mapping API.
+ *
+ * Drivers who need to acquire an scatter/gather table for objects need to call
+ * drm_gem_shmem_get_pages_sgt() instead.
+ *
+ * Returns:
+ * A pointer to the scatter/gather table of pinned pages or error pointer on failure.
+ */
+struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+
+	drm_WARN_ON(obj->dev, obj->import_attach);
+
+	return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SHIFT);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
+
+static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)
+{
+	struct drm_gem_object *obj = &shmem->base;
+	int ret;
+	struct sg_table *sgt;
+
+	if (shmem->sgt)
+		return shmem->sgt;
+
+	drm_WARN_ON(obj->dev, obj->import_attach);
+
+	ret = drm_gem_shmem_get_pages(shmem);
+	if (ret)
+		return ERR_PTR(ret);
+
+	sgt = drm_gem_shmem_get_sg_table(shmem);
+	if (IS_ERR(sgt)) {
+		ret = PTR_ERR(sgt);
+		goto err_put_pages;
+	}
+	/* Map the pages for use by the h/w. */
+	ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
+	if (ret)
+		goto err_free_sgt;
+
+	shmem->sgt = sgt;
+
+	return sgt;
+
+err_free_sgt:
+	sg_free_table(sgt);
+	kfree(sgt);
+err_put_pages:
+	drm_gem_shmem_put_pages(shmem);
+	return ERR_PTR(ret);
+}
+
+/**
+ * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
+ *				 scatter/gather table for a shmem GEM object.
+ * @shmem: shmem GEM object
+ *
+ * This function returns a scatter/gather table suitable for driver usage. If
+ * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg
+ * table created.
+ *
+ * This is the main function for drivers to get at backing storage, and it hides
+ * and difference between dma-buf imported and natively allocated objects.
+ * drm_gem_shmem_get_sg_table() should not be directly called by drivers.
+ *
+ * Returns:
+ * A pointer to the scatter/gather table of pinned pages or errno on failure.
+ */
+struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)
+{
+	int ret;
+	struct sg_table *sgt;
+
+	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
+	if (ret)
+		return ERR_PTR(ret);
+	sgt = drm_gem_shmem_get_pages_sgt_locked(shmem);
+	dma_resv_unlock(shmem->base.resv);
+
+	return sgt;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);
+
+/**
+ * drm_gem_shmem_prime_import_sg_table - Produce a shmem GEM object from
+ *                 another driver's scatter/gather table of pinned pages
+ * @dev: Device to import into
+ * @attach: DMA-BUF attachment
+ * @sgt: Scatter/gather table of pinned pages
+ *
+ * This function imports a scatter/gather table exported via DMA-BUF by
+ * another driver. Drivers that use the shmem helpers should set this as their
+ * &drm_driver.gem_prime_import_sg_table callback.
+ *
+ * Returns:
+ * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_object *
+drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
+				    struct dma_buf_attachment *attach,
+				    struct sg_table *sgt)
+{
+	size_t size = PAGE_ALIGN(attach->dmabuf->size);
+	struct drm_gem_shmem_object *shmem;
+
+	shmem = __drm_gem_shmem_create(dev, size, true);
+	if (IS_ERR(shmem))
+		return ERR_CAST(shmem);
+
+	shmem->sgt = sgt;
+
+	drm_dbg_prime(dev, "size = %zu\n", size);
+
+	return &shmem->base;
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
+
+MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
+MODULE_IMPORT_NS(DMA_BUF);
+MODULE_LICENSE("GPL v2");