drm/gem-vram: Do not pin buffer objects for vmap

Pin and vmap are distinct operations. Do not perform a pin as part
of the vmap call. This used to be necessary to keep the fbdev buffer
in place while it is being updated. Fbdev emulation has meanwhile
been fixed to lock the buffer correctly. Same for vunmap.

For refactoring the code, remove the pin calls from the helper's
vmap implementation in drm_gem_vram_vmap() and inline the call to
drm_gem_vram_kmap_locked(). This gives a vmap helper that only
maps the buffer object's memory pages without pinning or locking.
Do a similar refactoring for vunmap.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> # virtio-gpu
Acked-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240227113853.8464-13-tzimmermann@suse.de

drivers/gpu/drm/drm_gem_vram_helper.c

@@ -368,11 +368,28 @@ int drm_gem_vram_unpin(struct drm_gem_vram_object *gbo)
 }
 EXPORT_SYMBOL(drm_gem_vram_unpin);
 
-static int drm_gem_vram_kmap_locked(struct drm_gem_vram_object *gbo,
-				    struct iosys_map *map)
+/**
+ * drm_gem_vram_vmap() - Pins and maps a GEM VRAM object into kernel address
+ *                       space
+ * @gbo: The GEM VRAM object to map
+ * @map: Returns the kernel virtual address of the VRAM GEM object's backing
+ *       store.
+ *
+ * The vmap function pins a GEM VRAM object to its current location, either
+ * system or video memory, and maps its buffer into kernel address space.
+ * As pinned object cannot be relocated, you should avoid pinning objects
+ * permanently. Call drm_gem_vram_vunmap() with the returned address to
+ * unmap and unpin the GEM VRAM object.
+ *
+ * Returns:
+ * 0 on success, or a negative error code otherwise.
+ */
+int drm_gem_vram_vmap(struct drm_gem_vram_object *gbo, struct iosys_map *map)
 {
 	int ret;
 
+	dma_resv_assert_held(gbo->bo.base.resv);
+
 	if (gbo->vmap_use_count > 0)
 		goto out;
 
@@ -393,12 +410,23 @@ static int drm_gem_vram_kmap_locked(struct drm_gem_vram_object *gbo,
 
 	return 0;
 }
+EXPORT_SYMBOL(drm_gem_vram_vmap);
 
-static void drm_gem_vram_kunmap_locked(struct drm_gem_vram_object *gbo,
-				       struct iosys_map *map)
+/**
+ * drm_gem_vram_vunmap() - Unmaps and unpins a GEM VRAM object
+ * @gbo: The GEM VRAM object to unmap
+ * @map: Kernel virtual address where the VRAM GEM object was mapped
+ *
+ * A call to drm_gem_vram_vunmap() unmaps and unpins a GEM VRAM buffer. See
+ * the documentation for drm_gem_vram_vmap() for more information.
+ */
+void drm_gem_vram_vunmap(struct drm_gem_vram_object *gbo,
+			 struct iosys_map *map)
 {
 	struct drm_device *dev = gbo->bo.base.dev;
 
+	dma_resv_assert_held(gbo->bo.base.resv);
+
 	if (drm_WARN_ON_ONCE(dev, !gbo->vmap_use_count))
 		return;
 
@@ -415,60 +443,6 @@ static void drm_gem_vram_kunmap_locked(struct drm_gem_vram_object *gbo,
 	 * from memory. See drm_gem_vram_bo_driver_move_notify().
 	 */
 }
-
-/**
- * drm_gem_vram_vmap() - Pins and maps a GEM VRAM object into kernel address
- *                       space
- * @gbo: The GEM VRAM object to map
- * @map: Returns the kernel virtual address of the VRAM GEM object's backing
- *       store.
- *
- * The vmap function pins a GEM VRAM object to its current location, either
- * system or video memory, and maps its buffer into kernel address space.
- * As pinned object cannot be relocated, you should avoid pinning objects
- * permanently. Call drm_gem_vram_vunmap() with the returned address to
- * unmap and unpin the GEM VRAM object.
- *
- * Returns:
- * 0 on success, or a negative error code otherwise.
- */
-int drm_gem_vram_vmap(struct drm_gem_vram_object *gbo, struct iosys_map *map)
-{
-	int ret;
-
-	dma_resv_assert_held(gbo->bo.base.resv);
-
-	ret = drm_gem_vram_pin_locked(gbo, 0);
-	if (ret)
-		return ret;
-	ret = drm_gem_vram_kmap_locked(gbo, map);
-	if (ret)
-		goto err_drm_gem_vram_unpin_locked;
-
-	return 0;
-
-err_drm_gem_vram_unpin_locked:
-	drm_gem_vram_unpin_locked(gbo);
-	return ret;
-}
-EXPORT_SYMBOL(drm_gem_vram_vmap);
-
-/**
- * drm_gem_vram_vunmap() - Unmaps and unpins a GEM VRAM object
- * @gbo: The GEM VRAM object to unmap
- * @map: Kernel virtual address where the VRAM GEM object was mapped
- *
- * A call to drm_gem_vram_vunmap() unmaps and unpins a GEM VRAM buffer. See
- * the documentation for drm_gem_vram_vmap() for more information.
- */
-void drm_gem_vram_vunmap(struct drm_gem_vram_object *gbo,
-			 struct iosys_map *map)
-{
-	dma_resv_assert_held(gbo->bo.base.resv);
-
-	drm_gem_vram_kunmap_locked(gbo, map);
-	drm_gem_vram_unpin_locked(gbo);
-}
 EXPORT_SYMBOL(drm_gem_vram_vunmap);
 
 /**