drm/atomic-helper: Add {begin,end}_fb_access to plane helpers

Add {begin,end}_fb_access helpers to run at the beginning and end of
an atomic commit. The begin_fb_access helper acquires resources that
are necessary to perform the atomic commit. It it similar to prepare_fb,
except that the resources are to be released at the end of the commit.
Resources acquired by prepare_fb are held until after the next pageflip.

The end_fb_access helper performs the corresponding resource cleanup.
Atomic helpers call it with the new plane state. This is different from
cleanup_fb, which releases resources of the old plane state.

v2:
	* fix typos in commit message (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221025101737.8874-2-tzimmermann@suse.de

1 files changed, 9 insertions, 10 deletions

diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c b/drivers/gpu/drm/drm_gem_atomic_helper.c
index b6a0110eb64a..1de0a08afd86 100644
--- a/drivers/gpu/drm/drm_gem_atomic_helper.c
+++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
@@ -414,16 +414,14 @@ void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct drm_plane_state *
 EXPORT_SYMBOL(drm_gem_cleanup_shadow_fb);
 
 /**
- * drm_gem_simple_kms_prepare_shadow_fb - prepares shadow framebuffers
+ * drm_gem_simple_kms_begin_shadow_fb_access - prepares shadow framebuffers for CPU access
  * @pipe: the simple display pipe
  * @plane_state: the plane state of type struct drm_shadow_plane_state
  *
- * This function implements struct drm_simple_display_funcs.prepare_fb. It
- * maps all buffer objects of the plane's framebuffer into kernel address
- * space and stores them in struct drm_shadow_plane_state.map. The
- * framebuffer will be synchronized as part of the atomic commit.
+ * This function implements struct drm_simple_display_funcs.begin_fb_access.
  *
- * See drm_gem_simple_kms_cleanup_shadow_fb() for cleanup.
+ * See drm_gem_begin_shadow_fb_access() for details and
+ * drm_gem_simple_kms_cleanup_shadow_fb() for cleanup.
  *
  * Returns:
  * 0 on success, or a negative errno code otherwise.
@@ -436,14 +434,15 @@ int drm_gem_simple_kms_prepare_shadow_fb(struct drm_simple_display_pipe *pipe,
 EXPORT_SYMBOL(drm_gem_simple_kms_prepare_shadow_fb);
 
 /**
- * drm_gem_simple_kms_cleanup_shadow_fb - releases shadow framebuffers
+ * drm_gem_simple_kms_end_shadow_fb_access - releases shadow framebuffers from CPU access
  * @pipe: the simple display pipe
  * @plane_state: the plane state of type struct drm_shadow_plane_state
  *
- * This function implements struct drm_simple_display_funcs.cleanup_fb.
- * This function unmaps all buffer objects of the plane's framebuffer.
+ * This function implements struct drm_simple_display_funcs.end_fb_access.
+ * It undoes all effects of drm_gem_simple_kms_begin_shadow_fb_access() in
+ * reverse order.
  *
- * See drm_gem_simple_kms_prepare_shadow_fb().
+ * See drm_gem_simple_kms_begin_shadow_fb_access().
  */
 void drm_gem_simple_kms_cleanup_shadow_fb(struct drm_simple_display_pipe *pipe,
 					  struct drm_plane_state *plane_state)