[PATCH] drm/atomic: Unconfuse the old_state mess in commmit_tail

[Daniel Vetter <daniel.vetter@ffwll.ch>]

I totally butcherd the job on typing the kernel-doc for these, and no
one realized. Noticed by Russell. Maarten has a more complete approach
to this confusion, by making it more explicit what the new/old state
is, instead of this magic switching behaviour.

Cc: Liviu Dudau <liviu.dudau@arm.com>
Reported-by: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Fixes: 9f2a7950e77a ("drm/atomic-helper: nonblocking commit support")
Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tomeu Vizoso <tomeu.vizoso@gmail.com>
Cc: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c      | 66 ++++++++++++++++----------------
 include/drm/drm_modeset_helper_vtables.h | 12 ++++--
 2 files changed, 41 insertions(+), 37 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 0b16587cdc62..94cde2d3a2ce 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1005,7 +1005,7 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables);
 /**
  * drm_atomic_helper_wait_for_fences - wait for fences stashed in plane state
  * @dev: DRM device
- * @state: atomic state object with old state structures
+ * @old_state: atomic state object with old state structures
  * @pre_swap: if true, do an interruptible wait
  *
  * For implicit sync, driver should fish the exclusive fence out from the
@@ -1016,14 +1016,14 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables);
  * Returns zero if success or < 0 if dma_fence_wait() fails.
  */
 int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
-				      struct drm_atomic_state *state,
+				      struct drm_atomic_state *old_state,
 				      bool pre_swap)
 {
 	struct drm_plane *plane;
 	struct drm_plane_state *plane_state;
 	int i, ret;
 
-	for_each_plane_in_state(state, plane, plane_state, i) {
+	for_each_plane_in_state(old_state, plane, plane_state, i) {
 		if (!pre_swap)
 			plane_state = plane->state;
 
@@ -1147,7 +1147,7 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_vblanks);
 
 /**
  * drm_atomic_helper_commit_tail - commit atomic update to hardware
- * @state: new modeset state to be committed
+ * @old_state: atomic state object with old state structures
  *
  * This is the default implemenation for the ->atomic_commit_tail() hook of the
  * &drm_mode_config_helper_funcs vtable.
@@ -1158,53 +1158,53 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_vblanks);
  *
  * For drivers supporting runtime PM the recommended sequence is instead ::
  *
- *     drm_atomic_helper_commit_modeset_disables(dev, state);
+ *     drm_atomic_helper_commit_modeset_disables(dev, old_state);
  *
- *     drm_atomic_helper_commit_modeset_enables(dev, state);
+ *     drm_atomic_helper_commit_modeset_enables(dev, old_state);
  *
- *     drm_atomic_helper_commit_planes(dev, state,
+ *     drm_atomic_helper_commit_planes(dev, old_state,
  *                                     DRM_PLANE_COMMIT_ACTIVE_ONLY);
  *
  * for committing the atomic update to hardware.  See the kerneldoc entries for
  * these three functions for more details.
  */
-void drm_atomic_helper_commit_tail(struct drm_atomic_state *state)
+void drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
 {
-	struct drm_device *dev = state->dev;
+	struct drm_device *dev = old_state->dev;
 
-	drm_atomic_helper_commit_modeset_disables(dev, state);
+	drm_atomic_helper_commit_modeset_disables(dev, old_state);
 
-	drm_atomic_helper_commit_planes(dev, state, 0);
+	drm_atomic_helper_commit_planes(dev, old_state, 0);
 
-	drm_atomic_helper_commit_modeset_enables(dev, state);
+	drm_atomic_helper_commit_modeset_enables(dev, old_state);
 
-	drm_atomic_helper_commit_hw_done(state);
+	drm_atomic_helper_commit_hw_done(old_state);
 
-	drm_atomic_helper_wait_for_vblanks(dev, state);
+	drm_atomic_helper_wait_for_vblanks(dev, old_state);
 
-	drm_atomic_helper_cleanup_planes(dev, state);
+	drm_atomic_helper_cleanup_planes(dev, old_state);
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit_tail);
 
-static void commit_tail(struct drm_atomic_state *state)
+static void commit_tail(struct drm_atomic_state *old_state)
 {
-	struct drm_device *dev = state->dev;
+	struct drm_device *dev = old_state->dev;
 	struct drm_mode_config_helper_funcs *funcs;
 
 	funcs = dev->mode_config.helper_private;
 
-	drm_atomic_helper_wait_for_fences(dev, state, false);
+	drm_atomic_helper_wait_for_fences(dev, old_state, false);
 
-	drm_atomic_helper_wait_for_dependencies(state);
+	drm_atomic_helper_wait_for_dependencies(old_state);
 
 	if (funcs && funcs->atomic_commit_tail)
-		funcs->atomic_commit_tail(state);
+		funcs->atomic_commit_tail(old_state);
 	else
-		drm_atomic_helper_commit_tail(state);
+		drm_atomic_helper_commit_tail(old_state);
 
-	drm_atomic_helper_commit_cleanup_done(state);
+	drm_atomic_helper_commit_cleanup_done(old_state);
 
-	drm_atomic_state_put(state);
+	drm_atomic_state_put(old_state);
 }
 
 static void commit_work(struct work_struct *work)
@@ -1498,10 +1498,10 @@ static struct drm_crtc_commit *preceeding_commit(struct drm_crtc *crtc)
 
 /**
  * drm_atomic_helper_wait_for_dependencies - wait for required preceeding commits
- * @state: new modeset state to be committed
+ * @old_state: atomic state object with old state structures
  *
  * This function waits for all preceeding commits that touch the same CRTC as
- * @state to both be committed to the hardware (as signalled by
+ * @old_state to both be committed to the hardware (as signalled by
  * drm_atomic_helper_commit_hw_done) and executed by the hardware (as signalled
  * by calling drm_crtc_vblank_send_event on the event member of
  * &drm_crtc_state).
@@ -1509,7 +1509,7 @@ static struct drm_crtc_commit *preceeding_commit(struct drm_crtc *crtc)
  * This is part of the atomic helper support for nonblocking commits, see
  * drm_atomic_helper_setup_commit() for an overview.
  */
-void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *state)
+void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
 {
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *crtc_state;
@@ -1517,7 +1517,7 @@ void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *state)
 	int i;
 	long ret;
 
-	for_each_crtc_in_state(state, crtc, crtc_state, i) {
+	for_each_crtc_in_state(old_state, crtc, crtc_state, i) {
 		spin_lock(&crtc->commit_lock);
 		commit = preceeding_commit(crtc);
 		if (commit)
@@ -1584,16 +1584,16 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_hw_done);
 
 /**
  * drm_atomic_helper_commit_cleanup_done - signal completion of commit
- * @state: new modeset state to be committed
+ * @old_state: atomic state object with old state structures
  *
- * This signals completion of the atomic update @state, including any cleanup
- * work. If used, it must be called right before calling
+ * This signals completion of the atomic update @old_state, including any
+ * cleanup work. If used, it must be called right before calling
  * drm_atomic_state_put().
  *
  * This is part of the atomic helper support for nonblocking commits, see
  * drm_atomic_helper_setup_commit() for an overview.
  */
-void drm_atomic_helper_commit_cleanup_done(struct drm_atomic_state *state)
+void drm_atomic_helper_commit_cleanup_done(struct drm_atomic_state *old_state)
 {
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *crtc_state;
@@ -1601,8 +1601,8 @@ void drm_atomic_helper_commit_cleanup_done(struct drm_atomic_state *state)
 	int i;
 	long ret;
 
-	for_each_crtc_in_state(state, crtc, crtc_state, i) {
-		commit = state->crtcs[i].commit;
+	for_each_crtc_in_state(old_state, crtc, crtc_state, i) {
+		commit = old_state->crtcs[i].commit;
 		if (WARN_ON(!commit))
 			continue;
 
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 72478cf82147..e96d662ea572 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -999,10 +999,14 @@ struct drm_mode_config_helper_funcs {
 	 * to implement blocking and nonblocking commits easily. It is not used
 	 * by the atomic helpers
 	 *
-	 * This hook should first commit the given atomic state to the hardware.
-	 * But drivers can add more waiting calls at the start of their
-	 * implementation, e.g. to wait for driver-internal request for implicit
-	 * syncing, before starting to commit the update to the hardware.
+	 * This function is called when the new atomic state has already been
+	 * swapped into the various state pointers. The the passed in state therefore contains
+	 * copies of the old/previous state. This hook should commit the new
+	 * state into hardware. Note that the helpers have already waited for
+	 * preceedning atomic commits and fences, but drivers can add more
+	 * waiting calls at the start of their implementation, e.g. to wait for
+	 * driver-internal request for implicit syncing, before starting to
+	 * commit the update to the hardware.
 	 *
 	 * After the atomic update is committed to the hardware this hook needs
 	 * to call drm_atomic_helper_commit_hw_done(). Then wait for the upate
-- 
2.10.2

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