drm/i915/guc: Skip suspend/resume GuC action on platforms w/o GuC submission

On some platforms (e.g. KBL) that do not support GuC submission, but
the user enabled the GuC communication (e.g for HuC authentication)
calling the GuC EXIT_S_STATE action results in lose of ability to
enter RC6. We can remove the GuC suspend/resume entirely as we do
not need to save the GuC submission status.

Add intel_guc_submission_is_enabled() function to determine if
GuC submission is active.

v2: Do not suspend/resume the GuC on platforms that do not support
    Guc Submission.
v3: Fix typo, move suspend logic to remove goto.
v4: Use intel_guc_submission_is_enabled() to check GuC submission
    status.
v5: No need to look at engine to determine if submission is enabled.
    Squash fix + intel_guc_submission_is_enabled() patch into one.
v6: Move resume check into intel_guc_resume() for symmetry.
    Fix commit Fixes tag.
Reported-by: KiteStramuort <kitestramuort@autistici.org>
Reported-by: S. Zharkoff <s.zharkoff@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111594
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111623
Fixes: ffd5ce22 ("drm/i915/guc: Updates for GuC 32.0.3 firmware")
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceralo Spurio <daniele.ceraolospurio@intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Tomas Janousek <tomi@nomi.cz>
Signed-off-by: Don Hiatt <don.hiatt@intel.com>
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/20191115231538.1249-1-don.hiatt@intel.com

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

@@ -553,6 +553,13 @@ int intel_guc_suspend(struct intel_guc *guc)
 		GUC_POWER_D1, /* any value greater than GUC_POWER_D0 */
 	};
 
+	/*
+	 * If GuC communication is enabled but submission is not supported,
+	 * we do not need to suspend the GuC.
+	 */
+	if (!intel_guc_submission_is_enabled(guc))
+		return 0;
+
 	/*
 	 * The ENTER_S_STATE action queues the save/restore operation in GuC FW
 	 * and then returns, so waiting on the H2G is not enough to guarantee
@@ -610,6 +617,14 @@ int intel_guc_resume(struct intel_guc *guc)
 		GUC_POWER_D0,
 	};
 
+	/*
+	 * If GuC communication is enabled but submission is not supported,
+	 * we do not need to resume the GuC but we do need to enable the
+	 * GuC communication on resume (above).
+	 */
+	if (!intel_guc_submission_is_enabled(guc))
+		return 0;
+
 	return intel_guc_send(guc, action, ARRAY_SIZE(action));
 }
 

drivers/gpu/drm/i915/i915_drv.h

@@ -2036,4 +2036,10 @@ i915_coherent_map_type(struct drm_i915_private *i915)
 	return HAS_LLC(i915) ? I915_MAP_WB : I915_MAP_WC;
 }
 
+static inline bool intel_guc_submission_is_enabled(struct intel_guc *guc)
+{
+	return intel_guc_is_submission_supported(guc) &&
+		intel_guc_is_running(guc);
+}
+
 #endif