diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index d21b1f84b838..a1a35b6daaf9 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -963,6 +963,12 @@ struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
 !Edrivers/gpu/drm/drm_mm.c
 !Iinclude/drm/drm_mm.h
     </sect2>
+    <sect2>
+      <title>CMA Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers
+!Edrivers/gpu/drm/drm_gem_cma_helper.c
+!Iinclude/drm/drm_gem_cma_helper.h
+    </sect2>
   </sect1>
 
   <!-- Internals: mode setting -->
diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index 0316310e2cc4..7f986d7b8e22 100644
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -29,18 +29,31 @@
 #include <drm/drm_gem_cma_helper.h>
 #include <drm/drm_vma_manager.h>
 
-/*
+/**
+ * DOC: cma helpers
+ *
+ * The Contiguous Memory Allocator reserves a pool of memory at early boot
+ * that is used to service requests for large blocks of contiguous memory.
+ *
+ * The DRM GEM/CMA helpers use this allocator as a means to provide buffer
+ * objects that are physically contiguous in memory. This is useful for
+ * display drivers that are unable to map scattered buffers via an IOMMU.
+ */
+
+/**
  * __drm_gem_cma_create - Create a GEM CMA object without allocating memory
- * @drm: The drm device
- * @size: The GEM object size
+ * @drm: DRM device
+ * @size: size of the object to allocate
  *
- * This function creates and initializes a GEM CMA object of the given size, but
- * doesn't allocate any memory to back the object.
+ * This function creates and initializes a GEM CMA object of the given size,
+ * but doesn't allocate any memory to back the object.
  *
- * Return a struct drm_gem_cma_object* on success or ERR_PTR values on failure.
+ * Returns:
+ * A struct drm_gem_cma_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
  */
 static struct drm_gem_cma_object *
-__drm_gem_cma_create(struct drm_device *drm, unsigned int size)
+__drm_gem_cma_create(struct drm_device *drm, size_t size)
 {
 	struct drm_gem_cma_object *cma_obj;
 	struct drm_gem_object *gem_obj;
@@ -69,14 +82,21 @@ error:
 	return ERR_PTR(ret);
 }
 
-/*
+/**
  * drm_gem_cma_create - allocate an object with the given size
+ * @drm: DRM device
+ * @size: size of the object to allocate
  *
- * returns a struct drm_gem_cma_object* on success or ERR_PTR values
- * on failure.
+ * This function creates a CMA GEM object and allocates a contiguous chunk of
+ * memory as backing store. The backing memory has the writecombine attribute
+ * set.
+ *
+ * Returns:
+ * A struct drm_gem_cma_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
  */
 struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
-		unsigned int size)
+					      size_t size)
 {
 	struct drm_gem_cma_object *cma_obj;
 	int ret;
@@ -104,17 +124,26 @@ error:
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_create);
 
-/*
- * drm_gem_cma_create_with_handle - allocate an object with the given
- * size and create a gem handle on it
+/**
+ * drm_gem_cma_create_with_handle - allocate an object with the given size and
+ *     return a GEM handle to it
+ * @file_priv: DRM file-private structure to register the handle for
+ * @drm: DRM device
+ * @size: size of the object to allocate
+ * @handle: return location for the GEM handle
  *
- * returns a struct drm_gem_cma_object* on success or ERR_PTR values
- * on failure.
+ * This function creates a CMA GEM object, allocating a physically contiguous
+ * chunk of memory as backing store. The GEM object is then added to the list
+ * of object associated with the given file and a handle to it is returned.
+ *
+ * Returns:
+ * A struct drm_gem_cma_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
  */
-static struct drm_gem_cma_object *drm_gem_cma_create_with_handle(
-		struct drm_file *file_priv,
-		struct drm_device *drm, unsigned int size,
-		unsigned int *handle)
+static struct drm_gem_cma_object *
+drm_gem_cma_create_with_handle(struct drm_file *file_priv,
+			       struct drm_device *drm, size_t size,
+			       uint32_t *handle)
 {
 	struct drm_gem_cma_object *cma_obj;
 	struct drm_gem_object *gem_obj;
@@ -145,9 +174,14 @@ err_handle_create:
 	return ERR_PTR(ret);
 }
 
-/*
- * drm_gem_cma_free_object - (struct drm_driver)->gem_free_object callback
- * function
+/**
+ * drm_gem_cma_free_object - free resources associated with a CMA GEM object
+ * @gem_obj: GEM object to free
+ *
+ * This function frees the backing memory of the CMA GEM object, cleans up the
+ * GEM object state and frees the memory used to store the object itself.
+ * Drivers using the CMA helpers should set this as their DRM driver's
+ * ->gem_free_object() callback.
  */
 void drm_gem_cma_free_object(struct drm_gem_object *gem_obj)
 {
@@ -170,15 +204,23 @@ void drm_gem_cma_free_object(struct drm_gem_object *gem_obj)
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_free_object);
 
-/*
- * drm_gem_cma_dumb_create - (struct drm_driver)->dumb_create callback
- * function
+/**
+ * drm_gem_cma_dumb_create - create a dumb buffer object
+ * @file_priv: DRM file-private structure to create the dumb buffer for
+ * @drm: DRM device
+ * @args: IOCTL data
  *
- * This aligns the pitch and size arguments to the minimum required. wrap
- * this into your own function if you need bigger alignment.
+ * 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 ->dumb_create() callback.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
  */
 int drm_gem_cma_dumb_create(struct drm_file *file_priv,
-		struct drm_device *dev, struct drm_mode_create_dumb *args)
+			    struct drm_device *drm,
+			    struct drm_mode_create_dumb *args)
 {
 	struct drm_gem_cma_object *cma_obj;
 	int min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
@@ -189,18 +231,30 @@ int drm_gem_cma_dumb_create(struct drm_file *file_priv,
 	if (args->size < args->pitch * args->height)
 		args->size = args->pitch * args->height;
 
-	cma_obj = drm_gem_cma_create_with_handle(file_priv, dev,
-			args->size, &args->handle);
+	cma_obj = drm_gem_cma_create_with_handle(file_priv, drm, args->size,
+						 &args->handle);
 	return PTR_ERR_OR_ZERO(cma_obj);
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_dumb_create);
 
-/*
- * drm_gem_cma_dumb_map_offset - (struct drm_driver)->dumb_map_offset callback
- * function
+/**
+ * drm_gem_cma_dumb_map_offset - return the fake mmap offset for a CMA GEM
+ *     object
+ * @file_priv: DRM file-private structure containing the GEM object
+ * @drm: DRM device
+ * @handle: GEM object handle
+ * @offset: return location for the fake mmap offset
+ *
+ * This function look up an object by its handle and returns the fake mmap
+ * offset associated with it. Drivers using the CMA helpers should set this
+ * as their DRM driver's ->dumb_map_offset() callback.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
  */
 int drm_gem_cma_dumb_map_offset(struct drm_file *file_priv,
-		struct drm_device *drm, uint32_t handle, uint64_t *offset)
+				struct drm_device *drm, u32 handle,
+				u64 *offset)
 {
 	struct drm_gem_object *gem_obj;
 
@@ -208,7 +262,7 @@ int drm_gem_cma_dumb_map_offset(struct drm_file *file_priv,
 
 	gem_obj = drm_gem_object_lookup(drm, file_priv, handle);
 	if (!gem_obj) {
-		dev_err(drm->dev, "failed to lookup gem object\n");
+		dev_err(drm->dev, "failed to lookup GEM object\n");
 		mutex_unlock(&drm->struct_mutex);
 		return -EINVAL;
 	}
@@ -251,8 +305,20 @@ static int drm_gem_cma_mmap_obj(struct drm_gem_cma_object *cma_obj,
 	return ret;
 }
 
-/*
- * drm_gem_cma_mmap - (struct file_operation)->mmap callback function
+/**
+ * drm_gem_cma_mmap - memory-map a CMA GEM object
+ * @filp: file object
+ * @vma: VMA for the area to be mapped
+ *
+ * This function implements an augmented version of the GEM DRM file mmap
+ * operation for CMA objects: In addition to the usual GEM VMA setup it
+ * immediately faults in the entire object instead of using on-demaind
+ * faulting. Drivers which employ the CMA helpers should use this function
+ * as their ->mmap() handler in the DRM device file's file_operations
+ * structure.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
  */
 int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
 {
@@ -272,7 +338,16 @@ int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
 EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);
 
 #ifdef CONFIG_DEBUG_FS
-void drm_gem_cma_describe(struct drm_gem_cma_object *cma_obj, struct seq_file *m)
+/**
+ * drm_gem_cma_describe - describe a CMA GEM object for debugfs
+ * @cma_obj: CMA GEM object
+ * @m: debugfs file handle
+ *
+ * This function can be used to dump a human-readable representation of the
+ * CMA GEM object into a synthetic file.
+ */
+void drm_gem_cma_describe(struct drm_gem_cma_object *cma_obj,
+			  struct seq_file *m)
 {
 	struct drm_gem_object *obj = &cma_obj->base;
 	struct drm_device *dev = obj->dev;
@@ -291,7 +366,18 @@ void drm_gem_cma_describe(struct drm_gem_cma_object *cma_obj, struct seq_file *m
 EXPORT_SYMBOL_GPL(drm_gem_cma_describe);
 #endif
 
-/* low-level interface prime helpers */
+/**
+ * drm_gem_cma_prime_get_sg_table - provide a scatter/gather table of pinned
+ *     pages for a CMA GEM object
+ * @obj: GEM object
+ *
+ * This function exports a scatter/gather table suitable for PRIME usage by
+ * calling the standard DMA mapping API. Drivers using the CMA helpers should
+ * set this as their DRM driver's ->gem_prime_get_sg_table() callback.
+ *
+ * Returns:
+ * A pointer to the scatter/gather table of pinned pages or NULL on failure.
+ */
 struct sg_table *drm_gem_cma_prime_get_sg_table(struct drm_gem_object *obj)
 {
 	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
@@ -315,6 +401,23 @@ out:
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_prime_get_sg_table);
 
+/**
+ * drm_gem_cma_prime_import_sg_table - produce a CMA 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. Imported buffers must be physically contiguous in memory
+ * (i.e. the scatter/gather table must contain a single entry). Drivers that
+ * use the CMA helpers should set this as their DRM driver's
+ * ->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_cma_prime_import_sg_table(struct drm_device *dev,
 				  struct dma_buf_attachment *attach,
@@ -339,6 +442,18 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev,
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_prime_import_sg_table);
 
+/**
+ * drm_gem_cma_prime_mmap - memory-map an exported CMA GEM object
+ * @obj: GEM object
+ * @vma: VMA for the area to be mapped
+ *
+ * This function maps a buffer imported via DRM PRIME into a userspace
+ * process's address space. Drivers that use the CMA helpers should set this
+ * as their DRM driver's ->gem_prime_mmap() callback.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
 int drm_gem_cma_prime_mmap(struct drm_gem_object *obj,
 			   struct vm_area_struct *vma)
 {
@@ -357,6 +472,20 @@ int drm_gem_cma_prime_mmap(struct drm_gem_object *obj,
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_prime_mmap);
 
+/**
+ * drm_gem_cma_prime_vmap - map a CMA GEM object into the kernel's virtual
+ *     address space
+ * @obj: GEM object
+ *
+ * This function maps a buffer exported via DRM PRIME into the kernel's
+ * virtual address space. Since the CMA buffers are already mapped into the
+ * kernel virtual address space this simply returns the cached virtual
+ * address. Drivers using the CMA helpers should set this as their DRM
+ * driver's ->gem_prime_vmap() callback.
+ *
+ * Returns:
+ * The kernel virtual address of the CMA GEM object's backing store.
+ */
 void *drm_gem_cma_prime_vmap(struct drm_gem_object *obj)
 {
 	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
@@ -365,6 +494,17 @@ void *drm_gem_cma_prime_vmap(struct drm_gem_object *obj)
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_prime_vmap);
 
+/**
+ * drm_gem_cma_prime_vunmap - unmap a CMA GEM object from the kernel's virtual
+ *     address space
+ * @obj: GEM object
+ * @vaddr: kernel virtual address where the CMA GEM object was mapped
+ *
+ * This function removes a buffer exported via DRM PRIME from the kernel's
+ * virtual address space. This is a no-op because CMA buffers cannot be
+ * unmapped from kernel space. Drivers using the CMA helpers should set this
+ * as their DRM driver's ->gem_prime_vunmap() callback.
+ */
 void drm_gem_cma_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
 {
 	/* Nothing to do */
diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h
index 2ff35f3de9c5..873d4eb7f125 100644
--- a/include/drm/drm_gem_cma_helper.h
+++ b/include/drm/drm_gem_cma_helper.h
@@ -4,6 +4,13 @@
 #include <drm/drmP.h>
 #include <drm/drm_gem.h>
 
+/**
+ * struct drm_gem_cma_object - GEM object backed by CMA memory allocations
+ * @base: base GEM object
+ * @paddr: physical address of the backing memory
+ * @sgt: scatter/gather table for imported PRIME buffers
+ * @vaddr: kernel virtual address of the backing memory
+ */
 struct drm_gem_cma_object {
 	struct drm_gem_object base;
 	dma_addr_t paddr;
@@ -19,23 +26,25 @@ to_drm_gem_cma_obj(struct drm_gem_object *gem_obj)
 	return container_of(gem_obj, struct drm_gem_cma_object, base);
 }
 
-/* free gem object. */
+/* free GEM object */
 void drm_gem_cma_free_object(struct drm_gem_object *gem_obj);
 
-/* create memory region for drm framebuffer. */
+/* create memory region for DRM framebuffer */
 int drm_gem_cma_dumb_create(struct drm_file *file_priv,
-		struct drm_device *drm, struct drm_mode_create_dumb *args);
+			    struct drm_device *drm,
+			    struct drm_mode_create_dumb *args);
 
-/* map memory region for drm framebuffer to user space. */
+/* map memory region for DRM framebuffer to user space */
 int drm_gem_cma_dumb_map_offset(struct drm_file *file_priv,
-		struct drm_device *drm, uint32_t handle, uint64_t *offset);
+				struct drm_device *drm, u32 handle,
+				u64 *offset);
 
-/* set vm_flags and we can change the vm attribute to other one at here. */
+/* set vm_flags and we can change the VM attribute to other one at here */
 int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma);
 
-/* allocate physical memory. */
+/* allocate physical memory */
 struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
-		unsigned int size);
+					      size_t size);
 
 extern const struct vm_operations_struct drm_gem_cma_vm_ops;