[PATCH 2/2] drm/i915/guc: Skip suspend/resume GuC action on platforms w/o GuC submission

[don.hiatt at intel.com]

From: Don Hiatt <don.hiatt at intel.com>

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.

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.

Signed-off-by: Don Hiatt <don.hiatt at intel.com>
---
 drivers/gpu/drm/i915/gt/uc/intel_guc.c | 7 +++++++
 drivers/gpu/drm/i915/gt/uc/intel_uc.c  | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
index 019ae6486e8d..92d9305c0d73 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
+++ b/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
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
index 629b19377a29..4dd43b99a334 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
@@ -605,6 +605,14 @@ static int __uc_resume(struct intel_uc *uc, bool enable_communication)
 	if (enable_communication)
 		guc_enable_communication(guc);
 
+	/*
+	 * 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;
+
 	err = intel_guc_resume(guc);
 	if (err) {
 		DRM_DEBUG_DRIVER("Failed to resume GuC, err=%d", err);
-- 
2.20.1