drm/i915/huc: stall media submission until HuC is loaded

Wait on the fence to be signalled to avoid the submissions finding HuC
not yet loaded.

v2: use dedicaded wait_queue_entry for waiting in HuC load, as submitq
can't be re-used for it.
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Tony Ye <tony.ye@intel.com>
Acked-by: Tony Ye <tony.ye@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220928004145.745803-13-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/gt/uc/intel_huc.h

@@ -81,6 +81,12 @@ static inline bool intel_huc_is_loaded_by_gsc(const struct intel_huc *huc)
 	return huc->fw.loaded_via_gsc;
 }
 
+static inline bool intel_huc_wait_required(struct intel_huc *huc)
+{
+	return intel_huc_is_used(huc) && intel_huc_is_loaded_by_gsc(huc) &&
+	       !intel_huc_is_authenticated(huc);
+}
+
 void intel_huc_load_status(struct intel_huc *huc, struct drm_printer *p);
 
 #endif

drivers/gpu/drm/i915/i915_request.c

@@ -1621,6 +1621,20 @@ i915_request_await_object(struct i915_request *to,
 	return ret;
 }
 
+static void i915_request_await_huc(struct i915_request *rq)
+{
+	struct intel_huc *huc = &rq->context->engine->gt->uc.huc;
+
+	/* don't stall kernel submissions! */
+	if (!rcu_access_pointer(rq->context->gem_context))
+		return;
+
+	if (intel_huc_wait_required(huc))
+		i915_sw_fence_await_sw_fence(&rq->submit,
+					     &huc->delayed_load.fence,
+					     &rq->hucq);
+}
+
 static struct i915_request *
 __i915_request_ensure_parallel_ordering(struct i915_request *rq,
 					struct intel_timeline *timeline)
@@ -1702,6 +1716,16 @@ __i915_request_add_to_timeline(struct i915_request *rq)
 	struct intel_timeline *timeline = i915_request_timeline(rq);
 	struct i915_request *prev;
 
+	/*
+	 * Media workloads may require HuC, so stall them until HuC loading is
+	 * complete. Note that HuC not being loaded when a user submission
+	 * arrives can only happen when HuC is loaded via GSC and in that case
+	 * we still expect the window between us starting to accept submissions
+	 * and HuC loading completion to be small (a few hundred ms).
+	 */
+	if (rq->engine->class == VIDEO_DECODE_CLASS)
+		i915_request_await_huc(rq);
+
 	/*
 	 * Dependency tracking and request ordering along the timeline
 	 * is special cased so that we can eliminate redundant ordering

drivers/gpu/drm/i915/i915_request.h

@@ -348,6 +348,11 @@ struct i915_request {
 #define	GUC_PRIO_FINI	0xfe
 	u8 guc_prio;
 
+	/**
+	 * @hucq: wait queue entry used to wait on the HuC load to complete
+	 */
+	wait_queue_entry_t hucq;
+
 	I915_SELFTEST_DECLARE(struct {
 		struct list_head link;
 		unsigned long delay;