[PATCH 1/2] drm: Introduce DRM_BRIDGE_OP_UPSTREAM_FIRST to alter bridge init order

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DSI sink devices typically want the DSI host powered up and configured
before they are powered up. pre_enable is the place this would normally
happen, but they are called in reverse order from panel/connector towards
the encoder, which is the "wrong" order.

Add a new flag DRM_BRIDGE_OP_UPSTREAM_FIRST that any bridge can set
to swap the order of pre_enable (and post_disable) so that any upstream
bridges are called first to create the desired state.

eg:
- Panel
- Bridge 1
- Bridge 2 DRM_BRIDGE_OP_UPSTREAM_FIRST
- Bridge 3
- Encoder
Would result in pre_enable's being called as Panel, Bridge 1, Bridge 3,
Bridge 2.

Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_bridge.c | 197 +++++++++++++++++++++++++++++++++++++------
 include/drm/drm_bridge.h     |   8 ++
 2 files changed, 180 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index c96847fc0ebc..7c24e8340efa 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -522,21 +522,58 @@ EXPORT_SYMBOL(drm_bridge_chain_disable);
  * Calls &drm_bridge_funcs.post_disable op for all the bridges in the
  * encoder chain, starting from the first bridge to the last. These are called
  * after completing the encoder's prepare op.
+ * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the post_disable for
+ * that bridge will be called before the previous one to reverse the pre_enable
+ * calling direction.
  *
  * Note: the bridge passed should be the one closest to the encoder
  */
 void drm_bridge_chain_post_disable(struct drm_bridge *bridge)
 {
 	struct drm_encoder *encoder;
+	struct drm_bridge *next, *limit;
 
 	if (!bridge)
 		return;
 
 	encoder = bridge->encoder;
 	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		limit = NULL;
+
+		if (!list_is_last(&bridge->chain_node, &encoder->bridge_chain)) {
+			next = list_next_entry(bridge, chain_node);
+
+			if (next->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
+				limit = next;
+
+				list_for_each_entry_from(next, &encoder->bridge_chain,
+							 chain_node) {
+					if (!(next->ops &
+						DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
+						next = list_prev_entry(next, chain_node);
+						limit = next;
+						break;
+					}
+				}
+
+				list_for_each_entry_from_reverse(next, &encoder->bridge_chain,
+								 chain_node) {
+					if (next == bridge)
+						break;
+
+					if (next->funcs->post_disable)
+						next->funcs->post_disable(next);
+				}
+			}
+		}
+
 		if (bridge->funcs->post_disable)
 			bridge->funcs->post_disable(bridge);
+
+		if (limit)
+			bridge = limit;
 	}
+
 }
 EXPORT_SYMBOL(drm_bridge_chain_post_disable);
 
@@ -577,22 +614,53 @@ EXPORT_SYMBOL(drm_bridge_chain_mode_set);
  * Calls &drm_bridge_funcs.pre_enable op for all the bridges in the encoder
  * chain, starting from the last bridge to the first. These are called
  * before calling the encoder's commit op.
+ * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the pre_enable for
+ * the previous bridge will be called before pre_enable of this bridge.
  *
  * Note: the bridge passed should be the one closest to the encoder
  */
 void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
 {
 	struct drm_encoder *encoder;
-	struct drm_bridge *iter;
+	struct drm_bridge *iter, *next, *limit;
 
 	if (!bridge)
 		return;
 
 	encoder = bridge->encoder;
+
 	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
+			next = iter;
+			limit = bridge;
+			list_for_each_entry_from_reverse(next,
+							 &encoder->bridge_chain,
+							 chain_node) {
+				if (next == bridge)
+					break;
+
+				if (!(next->ops &
+					DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
+					limit = list_prev_entry(next, chain_node);
+					break;
+				}
+			}
+
+			list_for_each_entry_from(next, &encoder->bridge_chain, chain_node) {
+				if (next == iter)
+					break;
+
+				if (next->funcs->pre_enable)
+					next->funcs->pre_enable(next);
+			}
+		}
+
 		if (iter->funcs->pre_enable)
 			iter->funcs->pre_enable(iter);
 
+		if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST)
+			iter = limit;
+
 		if (iter == bridge)
 			break;
 	}
@@ -667,6 +735,25 @@ void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
 
+static void drm_atomic_bridge_call_post_disable(struct drm_bridge *bridge,
+						struct drm_atomic_state *old_state)
+{
+	if (bridge->funcs->atomic_post_disable) {
+		struct drm_bridge_state *old_bridge_state;
+
+		old_bridge_state =
+			drm_atomic_get_old_bridge_state(old_state,
+							bridge);
+		if (WARN_ON(!old_bridge_state))
+			return;
+
+		bridge->funcs->atomic_post_disable(bridge,
+						   old_bridge_state);
+	} else if (bridge->funcs->post_disable) {
+		bridge->funcs->post_disable(bridge);
+	}
+}
+
 /**
  * drm_atomic_bridge_chain_post_disable - cleans up after disabling all bridges
  *					  in the encoder chain
@@ -677,6 +764,9 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
  * &drm_bridge_funcs.post_disable) op for all the bridges in the encoder chain,
  * starting from the first bridge to the last. These are called after completing
  * &drm_encoder_helper_funcs.atomic_disable
+ * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the post_disable for
+ * that bridge will be called before the previous one to reverse the pre_enable
+ * calling direction.
  *
  * Note: the bridge passed should be the one closest to the encoder
  */
@@ -684,30 +774,69 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
 					  struct drm_atomic_state *old_state)
 {
 	struct drm_encoder *encoder;
+	struct drm_bridge *next, *limit;
 
 	if (!bridge)
 		return;
 
 	encoder = bridge->encoder;
+
 	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
-		if (bridge->funcs->atomic_post_disable) {
-			struct drm_bridge_state *old_bridge_state;
+		limit = NULL;
+
+		if (!list_is_last(&bridge->chain_node, &encoder->bridge_chain)) {
+			next = list_next_entry(bridge, chain_node);
+
+			if (next->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
+				limit = next;
+
+				list_for_each_entry_from(next, &encoder->bridge_chain,
+							 chain_node) {
+					if (!(next->ops &
+						DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
+						next = list_prev_entry(next, chain_node);
+						limit = next;
+						break;
+					}
+				}
+
+				list_for_each_entry_from_reverse(next, &encoder->bridge_chain,
+								 chain_node) {
+					if (next == bridge)
+						break;
+
+					drm_atomic_bridge_call_post_disable(next,
+									    old_state);
+				}
+			}
+		}
 
-			old_bridge_state =
-				drm_atomic_get_old_bridge_state(old_state,
-								bridge);
-			if (WARN_ON(!old_bridge_state))
-				return;
+		drm_atomic_bridge_call_post_disable(bridge, old_state);
 
-			bridge->funcs->atomic_post_disable(bridge,
-							   old_bridge_state);
-		} else if (bridge->funcs->post_disable) {
-			bridge->funcs->post_disable(bridge);
-		}
+		if (limit)
+			bridge = limit;
 	}
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
 
+static void drm_atomic_bridge_call_pre_enable(struct drm_bridge *bridge,
+					      struct drm_atomic_state *old_state)
+{
+	if (bridge->funcs->atomic_pre_enable) {
+		struct drm_bridge_state *old_bridge_state;
+
+		old_bridge_state =
+			drm_atomic_get_old_bridge_state(old_state,
+							bridge);
+		if (WARN_ON(!old_bridge_state))
+			return;
+
+		bridge->funcs->atomic_pre_enable(bridge, old_bridge_state);
+	} else if (bridge->funcs->pre_enable) {
+		bridge->funcs->pre_enable(bridge);
+	}
+}
+
 /**
  * drm_atomic_bridge_chain_pre_enable - prepares for enabling all bridges in
  *					the encoder chain
@@ -718,6 +847,8 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
  * &drm_bridge_funcs.pre_enable) op for all the bridges in the encoder chain,
  * starting from the last bridge to the first. These are called before calling
  * &drm_encoder_helper_funcs.atomic_enable
+ * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the pre_enable for
+ * the previous bridge will be called before pre_enable of this bridge.
  *
  * Note: the bridge passed should be the one closest to the encoder
  */
@@ -725,26 +856,42 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
 					struct drm_atomic_state *old_state)
 {
 	struct drm_encoder *encoder;
-	struct drm_bridge *iter;
+	struct drm_bridge *iter, *next, *limit;
 
 	if (!bridge)
 		return;
 
 	encoder = bridge->encoder;
+
 	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
-		if (iter->funcs->atomic_pre_enable) {
-			struct drm_bridge_state *old_bridge_state;
+		if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
+			next = iter;
+			limit = bridge;
+			list_for_each_entry_from_reverse(next,
+							 &encoder->bridge_chain,
+							 chain_node) {
+				if (next == bridge)
+					break;
+
+				if (!(next->ops &
+					DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
+					limit = list_prev_entry(next, chain_node);
+					break;
+				}
+			}
+
+			list_for_each_entry_from(next, &encoder->bridge_chain, chain_node) {
+				if (next == iter)
+					break;
+
+				drm_atomic_bridge_call_pre_enable(next, old_state);
+			}
+		}
 
-			old_bridge_state =
-				drm_atomic_get_old_bridge_state(old_state,
-								iter);
-			if (WARN_ON(!old_bridge_state))
-				return;
+		drm_atomic_bridge_call_pre_enable(iter, old_state);
 
-			iter->funcs->atomic_pre_enable(iter, old_bridge_state);
-		} else if (iter->funcs->pre_enable) {
-			iter->funcs->pre_enable(iter);
-		}
+		if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST)
+			iter = limit;
 
 		if (iter == bridge)
 			break;
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index f27b4060faa2..523ec9d8f3f8 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -725,6 +725,14 @@ enum drm_bridge_ops {
 	 * this flag shall implement the &drm_bridge_funcs->get_modes callback.
 	 */
 	DRM_BRIDGE_OP_MODES = BIT(3),
+	/**
+	 * @DRM_BRIDGE_OP_UPSTREAM_FIRST: The bridge can requires
+	 * that the upstream node pre_enable is called before its pre_enable,
+	 * and conversely for post_disables. This is most frequently a
+	 * requirement for DSI devices which need the host to be initialised
+	 * before them.
+	 */
+	DRM_BRIDGE_OP_UPSTREAM_FIRST = BIT(4),
 };
 
 /**
-- 
2.7.4




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