[PATCH v2 01/61] drm/simple-kms: Add create_plane_state hook

The simple-kms helper provides a reset_plane hook to let drivers
override the default plane reset. However, the reset hook is
overloaded: it is used to create the initial software state at probe
time, but also to reset both the hardware and software state during
suspend/resume. These two roles have different expectations, and
reset is not fallible which makes error handling difficult.

The atomic_create_state pattern was introduced to untangle this by
providing a hook that only allocates and initializes a pristine state
without any side effect.

Add a create_plane_state hook to struct
drm_simple_display_pipe_funcs. When provided,
drm_simple_kms_plane_reset() will use it to allocate a fresh state,
falling back to reset_plane and then to the default
drm_atomic_helper_plane_reset().

This will allow simple-kms drivers to be converted to the
atomic_create_state pattern.

Signed-off-by: Maxime Ripard <[email protected]>
---
 drivers/gpu/drm/drm_simple_kms_helper.c | 26 ++++++++++++++++++++++++--
 include/drm/drm_simple_kms_helper.h     |  1 +
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 8e1d07b9f1e3..528968ea5c4b 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -279,19 +279,41 @@ static const struct drm_plane_helper_funcs drm_simple_kms_plane_helper_funcs = {
 	.end_fb_access = drm_simple_kms_plane_end_fb_access,
 	.atomic_check = drm_simple_kms_plane_atomic_check,
 	.atomic_update = drm_simple_kms_plane_atomic_update,
 };
 
+static void drm_simple_kms_plane_destroy_state(struct drm_plane *plane,
+					       struct drm_plane_state *state);
+
 static void drm_simple_kms_plane_reset(struct drm_plane *plane)
 {
 	struct drm_simple_display_pipe *pipe;
 
 	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
-	if (!pipe->funcs || !pipe->funcs->reset_plane)
+	if (!pipe->funcs)
 		return drm_atomic_helper_plane_reset(plane);
 
-	return pipe->funcs->reset_plane(pipe);
+	if (pipe->funcs->create_plane_state) {
+		struct drm_plane_state *state;
+
+		if (plane->state) {
+			drm_simple_kms_plane_destroy_state(plane, plane->state);
+			plane->state = NULL;
+		}
+
+		state = pipe->funcs->create_plane_state(pipe);
+		if (WARN_ON(IS_ERR(state)))
+			return;
+
+		plane->state = state;
+		return;
+	}
+
+	if (pipe->funcs->reset_plane)
+		return pipe->funcs->reset_plane(pipe);
+
+	return drm_atomic_helper_plane_reset(plane);
 }
 
 static struct drm_plane_state *drm_simple_kms_plane_duplicate_state(struct drm_plane *plane)
 {
 	struct drm_simple_display_pipe *pipe;
diff --git a/include/drm/drm_simple_kms_helper.h b/include/drm/drm_simple_kms_helper.h
index cb672ce0e856..b58f6d532820 100644
--- a/include/drm/drm_simple_kms_helper.h
+++ b/include/drm/drm_simple_kms_helper.h
@@ -42,10 +42,11 @@ struct drm_simple_display_pipe_funcs {
 	void (*reset_crtc)(struct drm_simple_display_pipe *pipe);
 	struct drm_crtc_state * (*duplicate_crtc_state)(struct drm_simple_display_pipe *pipe);
 	void (*destroy_crtc_state)(struct drm_simple_display_pipe *pipe,
 				   struct drm_crtc_state *crtc_state);
 	void (*reset_plane)(struct drm_simple_display_pipe *pipe);
+	struct drm_plane_state * (*create_plane_state)(struct drm_simple_display_pipe *pipe);
 	struct drm_plane_state * (*duplicate_plane_state)(struct drm_simple_display_pipe *pipe);
 	void (*destroy_plane_state)(struct drm_simple_display_pipe *pipe,
 				    struct drm_plane_state *plane_state);
 };
 

-- 
2.55.0