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

[don.hiatt@intel.com]

From: Don Hiatt <don.hiatt@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/remove 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.

Signed-off-by: Don Hiatt <don.hiatt@intel.com>
---
 drivers/gpu/drm/i915/gt/uc/intel_uc.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
index 3fdbc935d155..04031564f0b1 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
@@ -572,10 +572,19 @@ void intel_uc_runtime_suspend(struct intel_uc *uc)
 	if (!intel_guc_is_running(guc))
 		return;
 
+	/*
+	 * If GuC communciation is enabled but submission is not supported,
+	 * we do not need to suspend the GuC but we do need to disable the
+	 * GuC communication on suspend.
+	 */
+	if (!guc->submission_supported)
+		goto guc_disable_comm;
+
 	err = intel_guc_suspend(guc);
 	if (err)
 		DRM_DEBUG_DRIVER("Failed to suspend GuC, err=%d", err);
 
+guc_disable_comm:
 	guc_disable_communication(guc);
 }
 
@@ -605,6 +614,14 @@ static int __uc_resume(struct intel_uc *uc, bool enable_communication)
 	if (enable_communication)
 		guc_enable_communication(guc);
 
+	/*
+	 * If GuC communciation 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 (!guc->submission_supported)
+		return 0;
+
 	err = intel_guc_resume(guc);
 	if (err) {
 		DRM_DEBUG_DRIVER("Failed to resume GuC, err=%d", err);
-- 
2.20.1

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