drm/i915/guc: Use dedicated flag to track submission mode

Instead of relying on enable_guc modparam to represent actual
GuC submission mode, use dedicated flag and look at modparam
only to check if submission was explicitly disabled by the user.

v2: rebased, simplified condition (Chris)
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190731223321.36436-4-michal.wajdeczko@intel.com

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

@@ -82,6 +82,7 @@ void intel_guc_init_early(struct intel_guc *guc)
 	intel_guc_fw_init_early(guc);
 	intel_guc_ct_init_early(&guc->ct);
 	intel_guc_log_init_early(&guc->log);
+	intel_guc_submission_init_early(guc);
 
 	mutex_init(&guc->send_mutex);
 	spin_lock_init(&guc->irq_lock);

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

@@ -61,6 +61,8 @@ struct intel_guc {
 		void (*disable)(struct intel_guc *guc);
 	} interrupts;
 
+	bool submission_supported;
+
 	struct i915_vma *ads_vma;
 	struct __guc_ads_blob *ads_blob;
 
@@ -190,6 +192,11 @@ static inline int intel_guc_sanitize(struct intel_guc *guc)
 	return 0;
 }
 
+static inline bool intel_guc_is_submission_supported(struct intel_guc *guc)
+{
+	return guc->submission_supported;
+}
+
 static inline void intel_guc_enable_msg(struct intel_guc *guc, u32 mask)
 {
 	spin_lock_irq(&guc->irq_lock);

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

@@ -1163,6 +1163,22 @@ void intel_guc_submission_disable(struct intel_guc *guc)
 	guc_clients_disable(guc);
 }
 
+static bool __guc_submission_support(struct intel_guc *guc)
+{
+	/* XXX: GuC submission is unavailable for now */
+	return false;
+
+	if (!intel_guc_is_supported(guc))
+		return false;
+
+	return i915_modparams.enable_guc & ENABLE_GUC_SUBMISSION;
+}
+
+void intel_guc_submission_init_early(struct intel_guc *guc)
+{
+	guc->submission_supported = __guc_submission_support(guc);
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftest_guc.c"
 #endif

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

@@ -77,6 +77,7 @@ struct intel_guc_client {
 	I915_SELFTEST_DECLARE(bool use_nop_wqi);
 };
 
+void intel_guc_submission_init_early(struct intel_guc *guc);
 int intel_guc_submission_init(struct intel_guc *guc);
 int intel_guc_submission_enable(struct intel_guc *guc);
 void intel_guc_submission_disable(struct intel_guc *guc);

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

@@ -56,8 +56,7 @@ static inline bool intel_uc_supports_guc(struct intel_uc *uc)
 
 static inline bool intel_uc_supports_guc_submission(struct intel_uc *uc)
 {
-	GEM_BUG_ON(i915_modparams.enable_guc < 0);
-	return i915_modparams.enable_guc & ENABLE_GUC_SUBMISSION;
+	return intel_guc_is_submission_supported(&uc->guc);
 }
 
 static inline bool intel_uc_supports_huc(struct intel_uc *uc)