[RFC PATCH] drm/i915: Don't reset GuC before engine reset on full GT reset

[Nirmoy Das <nirmoy.das@xxxxxxxxx>]

Currently intel_gt_reset() happens as follows:

reset_prepare() ---> Sends GDRST to GuC, GuC is in GS_MIA_IN_RESET
do_reset()
	__intel_gt_reset()
		*_engine_reset_prepare() -->RESET_CTL expects running
		GuC
		*_reset_engines()
intel_gt_init_hw() --> GuC FW loading happens, GuC comes out of
GS_MIA_IN_RESET.

Fix the above flow so that GuC reset happens after all the
engines reset is done.

Cc: John Harrison <John.C.Harrison@xxxxxxxxx>
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/intel_reset.c |  9 ++++--
 drivers/gpu/drm/i915/gt/uc/intel_uc.c | 42 +++++++++++++++++++++------
 drivers/gpu/drm/i915/gt/uc/intel_uc.h |  1 +
 3 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index c8e9aa41fdea..9ebd68ce0c22 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -879,8 +879,11 @@ static intel_engine_mask_t reset_prepare(struct intel_gt *gt)
 	intel_engine_mask_t awake = 0;
 	enum intel_engine_id id;
 
-	/* For GuC mode, ensure submission is disabled before stopping ring */
-	intel_uc_reset_prepare(&gt->uc);
+	/*
+	 * For GuC mode, ensure submission is disabled before stopping ring.
+	 * Don't reset the GuC a engine reset requires GuC to be running.
+	 */
+	intel_uc_reset_prepare_without_guc_reset(&gt->uc);
 
 	for_each_engine(engine, gt, id) {
 		if (intel_engine_pm_get_if_awake(engine))
@@ -1227,6 +1230,8 @@ void intel_gt_reset(struct intel_gt *gt,
 
 	intel_overlay_reset(gt->i915);
 
+	/* Now that all engines are clean, Reset the GuC */
+	intel_uc_reset_prepare(&gt->uc);
 	/*
 	 * Next we need to restore the context, but we don't use those
 	 * yet either...
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
index 7a63abf8f644..5feee4db2ccc 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
@@ -345,7 +345,7 @@ static void __uc_fini(struct intel_uc *uc)
 	intel_guc_fini(&uc->guc);
 }
 
-static int __uc_sanitize(struct intel_uc *uc)
+static void __uc_sanitize_without_guc_reset(struct intel_uc *uc)
 {
 	struct intel_guc *guc = &uc->guc;
 	struct intel_huc *huc = &uc->huc;
@@ -354,7 +354,11 @@ static int __uc_sanitize(struct intel_uc *uc)
 
 	intel_huc_sanitize(huc);
 	intel_guc_sanitize(guc);
+}
 
+static int __uc_sanitize(struct intel_uc *uc)
+{
+	__uc_sanitize_without_guc_reset(uc);
 	return __intel_uc_reset_hw(uc);
 }
 
@@ -593,13 +597,7 @@ static void __uc_fini_hw(struct intel_uc *uc)
 	__uc_sanitize(uc);
 }
 
-/**
- * intel_uc_reset_prepare - Prepare for reset
- * @uc: the intel_uc structure
- *
- * Preparing for full gpu reset.
- */
-void intel_uc_reset_prepare(struct intel_uc *uc)
+static void __intel_uc_reset_prepare(struct intel_uc *uc, bool reset_guc)
 {
 	struct intel_guc *guc = &uc->guc;
 
@@ -617,9 +615,35 @@ void intel_uc_reset_prepare(struct intel_uc *uc)
 		intel_guc_submission_reset_prepare(guc);
 
 sanitize:
-	__uc_sanitize(uc);
+	if (reset_guc)
+		__uc_sanitize(uc);
+	else
+		__uc_sanitize_without_guc_reset(uc);
 }
 
+/**
+ * intel_uc_reset_prepare - Prepare for reset
+ * @uc: the intel_uc structure
+ *
+ * Preparing for full gpu reset.
+ */
+void intel_uc_reset_prepare(struct intel_uc *uc)
+{
+	__intel_uc_reset_prepare(uc, true);
+}
+/**
+ * intel_uc_reset_prepare_without_guc_reset - Prepare for reset but don't reset
+ * the GuC
+ * @uc: the intel_uc structure
+ *
+ * Preparing for full gpu reset.
+ */
+void intel_uc_reset_prepare_without_guc_reset(struct intel_uc *uc)
+{
+	__intel_uc_reset_prepare(uc, false);
+}
+
+
 void intel_uc_reset(struct intel_uc *uc, intel_engine_mask_t stalled)
 {
 	struct intel_guc *guc = &uc->guc;
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.h b/drivers/gpu/drm/i915/gt/uc/intel_uc.h
index 014bb7d83689..9d6191ece498 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.h
@@ -46,6 +46,7 @@ void intel_uc_driver_late_release(struct intel_uc *uc);
 void intel_uc_driver_remove(struct intel_uc *uc);
 void intel_uc_init_mmio(struct intel_uc *uc);
 void intel_uc_reset_prepare(struct intel_uc *uc);
+void intel_uc_reset_prepare_without_guc_reset(struct intel_uc *uc);
 void intel_uc_reset(struct intel_uc *uc, intel_engine_mask_t stalled);
 void intel_uc_reset_finish(struct intel_uc *uc);
 void intel_uc_cancel_requests(struct intel_uc *uc);
-- 
2.42.0