drm/i915/guc: Implement parallel context pin / unpin functions

Parallel contexts are perma-pinned by the upper layers which makes the
backend implementation rather simple. The parent pins the guc_id and
children increment the parent's pin count on pin to ensure all the
contexts are unpinned before we disable scheduling with the GuC / or
deregister the context.

v2:
 (Daniel Vetter)
  - Perma-pin parallel contexts
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211014172005.27155-12-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -2584,6 +2584,76 @@ static const struct intel_context_ops virtual_guc_context_ops = {
 	.get_sibling = guc_virtual_get_sibling,
 };
 
+/* Future patches will use this function */
+__maybe_unused
+static int guc_parent_context_pin(struct intel_context *ce, void *vaddr)
+{
+	struct intel_engine_cs *engine = guc_virtual_get_sibling(ce->engine, 0);
+	struct intel_guc *guc = ce_to_guc(ce);
+	int ret;
+
+	GEM_BUG_ON(!intel_context_is_parent(ce));
+	GEM_BUG_ON(!intel_engine_is_virtual(ce->engine));
+
+	ret = pin_guc_id(guc, ce);
+	if (unlikely(ret < 0))
+		return ret;
+
+	return __guc_context_pin(ce, engine, vaddr);
+}
+
+/* Future patches will use this function */
+__maybe_unused
+static int guc_child_context_pin(struct intel_context *ce, void *vaddr)
+{
+	struct intel_engine_cs *engine = guc_virtual_get_sibling(ce->engine, 0);
+
+	GEM_BUG_ON(!intel_context_is_child(ce));
+	GEM_BUG_ON(!intel_engine_is_virtual(ce->engine));
+
+	__intel_context_pin(ce->parallel.parent);
+	return __guc_context_pin(ce, engine, vaddr);
+}
+
+/* Future patches will use this function */
+__maybe_unused
+static void guc_parent_context_unpin(struct intel_context *ce)
+{
+	struct intel_guc *guc = ce_to_guc(ce);
+
+	GEM_BUG_ON(context_enabled(ce));
+	GEM_BUG_ON(intel_context_is_barrier(ce));
+	GEM_BUG_ON(!intel_context_is_parent(ce));
+	GEM_BUG_ON(!intel_engine_is_virtual(ce->engine));
+
+	unpin_guc_id(guc, ce);
+	lrc_unpin(ce);
+}
+
+/* Future patches will use this function */
+__maybe_unused
+static void guc_child_context_unpin(struct intel_context *ce)
+{
+	GEM_BUG_ON(context_enabled(ce));
+	GEM_BUG_ON(intel_context_is_barrier(ce));
+	GEM_BUG_ON(!intel_context_is_child(ce));
+	GEM_BUG_ON(!intel_engine_is_virtual(ce->engine));
+
+	lrc_unpin(ce);
+}
+
+/* Future patches will use this function */
+__maybe_unused
+static void guc_child_context_post_unpin(struct intel_context *ce)
+{
+	GEM_BUG_ON(!intel_context_is_child(ce));
+	GEM_BUG_ON(!intel_context_is_pinned(ce->parallel.parent));
+	GEM_BUG_ON(!intel_engine_is_virtual(ce->engine));
+
+	lrc_post_unpin(ce);
+	intel_context_unpin(ce->parallel.parent);
+}
+
 static bool
 guc_irq_enable_breadcrumbs(struct intel_breadcrumbs *b)
 {