[PATCH RFC] drm/atomic: Disable planes on blanked CRTC and enable on unblank

[Jyri Sarha]

Disable planes if they are on to be blanked CRTC and enable them when
the CRTC is turned back on by DMPS.

This is desirable on HW that loses its context on blanking. When
planes are enabled and disabled with the associated CRTCs, there is no
need to restore the plane context in runtime_resume callback.

Signed-off-by: Jyri Sarha <jsarha at ti.com>
---
We would need something like this to get rid off OMAPDSS somewhat
messy runtime_resume code. How does this look, could this generic
solution be refined to be acceptable to mainline, or should we start
looking a local solution to omapdrm?

BTW, with this patch the planes are sometimes disabled multiple
times. So probably a boolean (or maybe two like on crtc) should be
added to drm_plane_state to track and avoid multiple shutdowns.

 drivers/gpu/drm/drm_atomic_helper.c | 19 +++++++++++++++++--
 include/drm/drm_atomic_helper.h     |  7 +++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index aecb5d6..92fcaef 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1994,8 +1994,8 @@ EXPORT_SYMBOL(drm_atomic_helper_page_flip);
  *
  * This is the main helper function provided by the atomic helper framework for
  * implementing the legacy DPMS connector interface. It computes the new desired
- * ->active state for the corresponding CRTC (if the connector is enabled) and
- *  updates it.
+ * ->active state for the corresponding CRTC and planes on it (if the connector
+ * is enabled) and updates it.
  *
  * Returns:
  * Returns 0 on success, negative errno numbers on failure.
@@ -2008,6 +2008,7 @@ int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
 	struct drm_crtc_state *crtc_state;
 	struct drm_crtc *crtc;
 	struct drm_connector *tmp_connector;
+	struct drm_plane *tmp_plane;
 	int ret;
 	bool active = false;
 	int old_mode = connector->dpms;
@@ -2046,6 +2047,20 @@ retry:
 	}
 	crtc_state->active = active;
 
+	/* Collect associated plane states to global state object. */
+	list_for_each_entry(tmp_plane, &config->plane_list, head) {
+		struct drm_plane_state *plane_state;
+
+		if (tmp_plane->state->crtc != crtc)
+			continue;
+
+		plane_state = drm_atomic_get_plane_state(state, tmp_plane);
+		if (IS_ERR(plane_state)) {
+			ret = PTR_ERR(plane_state);
+			goto fail;
+		}
+	}
+
 	ret = drm_atomic_commit(state);
 	if (ret != 0)
 		goto fail;
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 11266d14..89c327f 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -173,6 +173,13 @@ drm_atomic_plane_disabling(struct drm_plane *plane,
 		(plane->state->crtc != NULL && plane->state->fb == NULL));
 
 	/*
+	 * If the plane is on a crtc that is not going to be active the plane
+	 * it self can be disabled too.
+	 */
+	if (plane->state->crtc && !plane->state->crtc->state->active)
+		return true;
+
+	/*
 	 * When using the transitional helpers, old_state may be NULL. If so,
 	 * we know nothing about the current state and have to assume that it
 	 * might be enabled.
-- 
1.9.1