drm/msm: Initialize mmap offset after constructing the buffer object

Only the msm driver provides its own implementation of gem_prime_mmap
from struct drm_driver. All other drivers use the drm_gem_prime_mmap()
helper.

Initialize the mmap offset when constructing the buffer object in msm
and reduce the gem_prime_mmap code to the generic helper. Prepares
msm for the removal of struct drm_driver.gem_prime_mmap.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613150441.17720-2-tzimmermann@suse.de

drivers/gpu/drm/msm/msm_gem.c

@@ -1240,6 +1240,10 @@ struct drm_gem_object *msm_gem_new(struct drm_device *dev, uint32_t size, uint32
 	list_add_tail(&msm_obj->node, &priv->objects);
 	mutex_unlock(&priv->obj_lock);
 
+	ret = drm_gem_create_mmap_offset(obj);
+	if (ret)
+		goto fail;
+
 	return obj;
 
 fail:
@@ -1296,6 +1300,10 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,
 	list_add_tail(&msm_obj->node, &priv->objects);
 	mutex_unlock(&priv->obj_lock);
 
+	ret = drm_gem_create_mmap_offset(obj);
+	if (ret)
+		goto fail;
+
 	return obj;
 
 fail:

drivers/gpu/drm/msm/msm_gem_prime.c

@@ -13,16 +13,6 @@
 
 int msm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 {
-	int ret;
-
-	/* Ensure the mmap offset is initialized.  We lazily initialize it,
-	 * so if it has not been first mmap'd directly as a GEM object, the
-	 * mmap offset will not be already initialized.
-	 */
-	ret = drm_gem_create_mmap_offset(obj);
-	if (ret)
-		return ret;
-
 	return drm_gem_prime_mmap(obj, vma);
 }