[RFC PATCH 16/42] drm/i915/guc: Introduce context parent-child relationship

[Matthew Brost <matthew.brost@intel.com>]

Introduce context parent-child relationship. Once this relationship is
created all pinning / unpinning operations are directed to the parent
context. The parent context is responsible for pinning all of its'
children and itself.

This is a precursor to the full GuC multi-lrc implementation but aligns
to how GuC mutli-lrc interface is defined - a single H2G is used
register / deregister all of the contexts simultaneously.

Subsequent patches in the series will implement the pinning / unpinning
operations for parent / child contexts.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_context.c       | 29 +++++++++++++++++++
 drivers/gpu/drm/i915/gt/intel_context.h       | 18 ++++++++++++
 drivers/gpu/drm/i915/gt/intel_context_types.h | 12 ++++++++
 3 files changed, 59 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index b1e3d00fb1f2..76dd038c57d2 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -399,6 +399,8 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
 	spin_lock_init(&ce->guc_state.lock);
 	INIT_LIST_HEAD(&ce->guc_state.fences);
 
+	INIT_LIST_HEAD(&ce->guc_child_list);
+
 	spin_lock_init(&ce->guc_active.lock);
 	INIT_LIST_HEAD(&ce->guc_active.requests);
 
@@ -414,10 +416,17 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
 
 void intel_context_fini(struct intel_context *ce)
 {
+	struct intel_context *child, *next;
+
 	if (ce->timeline)
 		intel_timeline_put(ce->timeline);
 	i915_vm_put(ce->vm);
 
+	/* Need to put the creation ref for the children */
+	if (intel_context_is_parent(ce))
+		for_each_child_safe(ce, child, next)
+			intel_context_put(child);
+
 	mutex_destroy(&ce->pin_mutex);
 	i915_active_fini(&ce->active);
 }
@@ -544,6 +553,26 @@ struct i915_request *intel_context_find_active_request(struct intel_context *ce)
 	return active;
 }
 
+void intel_context_bind_parent_child(struct intel_context *parent,
+				     struct intel_context *child)
+{
+	/*
+	 * Callers responsibility to validate that this function is used
+	 * correctly but we use GEM_BUG_ON here ensure that they do.
+	 */
+	GEM_BUG_ON(!intel_engine_uses_guc(parent->engine));
+	GEM_BUG_ON(intel_context_is_pinned(parent));
+	GEM_BUG_ON(intel_context_is_child(parent));
+	GEM_BUG_ON(intel_context_is_pinned(child));
+	GEM_BUG_ON(intel_context_is_child(child));
+	GEM_BUG_ON(intel_context_is_parent(child));
+
+        parent->guc_number_children++;
+        list_add_tail(&child->guc_child_link,
+		      &parent->guc_child_list);
+	child->parent = parent;
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftest_context.c"
 #endif
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index 876bdb08303c..28378fd9eb99 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -41,6 +41,24 @@ void intel_context_free(struct intel_context *ce);
 int intel_context_reconfigure_sseu(struct intel_context *ce,
 				   const struct intel_sseu sseu);
 
+static inline bool intel_context_is_child(struct intel_context *ce)
+{
+	return !!ce->parent;
+}
+
+static inline bool intel_context_is_parent(struct intel_context *ce)
+{
+	return !!ce->guc_number_children;
+}
+
+void intel_context_bind_parent_child(struct intel_context *parent,
+				     struct intel_context *child);
+
+#define for_each_child(parent, ce)\
+	list_for_each_entry(ce, &parent->guc_child_list, guc_child_link)
+#define for_each_child_safe(parent, ce, cn)\
+	list_for_each_entry_safe(ce, cn, &parent->guc_child_list, guc_child_link)
+
 /**
  * intel_context_lock_pinned - Stablises the 'pinned' status of the HW context
  * @ce - the context
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index aabc1b349044..c2e66acaf892 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -202,6 +202,18 @@ struct intel_context {
 	/* GuC context blocked fence */
 	struct i915_sw_fence guc_blocked;
 
+	/* Head of children list or link in parent's children list */
+	union {
+		struct list_head guc_child_list;	/* parent */
+		struct list_head guc_child_link;	/* child */
+	};
+
+	/* Pointer to parent */
+	struct intel_context *parent;
+
+	/* Number of children if parent */
+	u8 guc_number_children;
+
 	/*
 	 * GuC priority management
 	 */
-- 
2.28.0