[Intel-gfx] [RFC PATCH 79/97] drm/i915/guc: Don't call ring_is_idle in GuC submission

[Matthew Brost]

The engine registers really shouldn't be touched during GuC submission
as the GuC owns the registers. Don't call ring_is_idle and tie
intel_engine_is_idle strickly the engine pm.

Because intel_engine_is_idle tied to the engine pm, retire requests
before checking intel_engines_are_idle in gt_drop_caches, and lastly
increase the timeout in gt_drop_caches for the intel_engines_are_idle
check.

Signed-off-by: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 13 +++++++++++++
 drivers/gpu/drm/i915/i915_debugfs.c       |  6 +++---
 drivers/gpu/drm/i915/i915_drv.h           |  2 +-
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index e34a61600c8c..591226b96201 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1226,6 +1226,9 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
 {
 	bool idle = true;
 
+	/* GuC submission shouldn't access HEAD & TAIL via MMIO */
+	GEM_BUG_ON(intel_engine_uses_guc(engine));
+
 	if (I915_SELFTEST_ONLY(!engine->mmio_base))
 		return true;
 
@@ -1292,6 +1295,16 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 	if (!i915_sched_engine_is_empty(engine->sched_engine))
 		return false;
 
+	/*
+	 * We shouldn't touch engine registers with GuC submission as the GuC
+	 * owns the registers. Let's tie the idle to engine pm, at worst this
+	 * function sometimes will falsely report non-idle when idle during the
+	 * delay to retire requests or with virtual engines and a request
+	 * running on another instance within the same class / submit mask.
+	 */
+	if (intel_engine_uses_guc(engine))
+		return false;
+
 	/* Ring stopped? */
 	return ring_is_idle(engine);
 }
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index d540dd8029d0..2639961504b5 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -867,13 +867,13 @@ gt_drop_caches(struct intel_gt *gt, u64 val)
 {
 	int ret;
 
+	if (val & DROP_RETIRE || val & DROP_RESET_ACTIVE)
+		intel_gt_retire_requests(gt);
+
 	if (val & DROP_RESET_ACTIVE &&
 	    wait_for(intel_engines_are_idle(gt), I915_IDLE_ENGINES_TIMEOUT))
 		intel_gt_set_wedged(gt);
 
-	if (val & DROP_RETIRE)
-		intel_gt_retire_requests(gt);
-
 	if (val & (DROP_IDLE | DROP_ACTIVE)) {
 		ret = intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
 		if (ret)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 3cfa6effbb5f..aa359b8480cd 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -576,7 +576,7 @@ struct i915_gem_mm {
 	u32 shrink_count;
 };
 
-#define I915_IDLE_ENGINES_TIMEOUT (200) /* in ms */
+#define I915_IDLE_ENGINES_TIMEOUT (500) /* in ms */
 
 unsigned long i915_fence_context_timeout(const struct drm_i915_private *i915,
 					 u64 context);
-- 
2.28.0