From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 15 Feb 2018 16:25:53 +0000
Subject: drm/i915: Assert that we always complete a submission to guc/execlists
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Git-commit: 339ccd35b42cb679b1a218fdbac4c029058c671c
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

The continual resubmission model for execlists (and emulated over guc)
requires that we keep feeding requests into the HW in order to generate
more CS interrupts to drain the rest of the queue. Add a couple of
asserts to ensure that we don't skip a cycle and come to a grinding
halt.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180215162553.23348-1-chris@chris-wilson.co.uk

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/i915/intel_guc_submission.c |    6 ++++++
 drivers/gpu/drm/i915/intel_lrc.c            |    6 ++++++
 2 files changed, 12 insertions(+)

--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -747,6 +747,12 @@ done:
 		execlists_set_active(execlists, EXECLISTS_ACTIVE_USER);
 		guc_submit(engine);
 	}
+
+	/* We must always keep the beast fed if we have work piled up */
+	GEM_BUG_ON(port_isset(execlists->port) &&
+		   !execlists_is_active(execlists, EXECLISTS_ACTIVE_USER));
+	GEM_BUG_ON(execlists->first && !port_isset(execlists->port));
+
 unlock:
 	spin_unlock_irq(&engine->timeline->lock);
 }
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -642,6 +642,12 @@ done:
 	execlists->first = rb;
 	if (submit)
 		port_assign(port, last);
+
+	/* We must always keep the beast fed if we have work piled up */
+	GEM_BUG_ON(port_isset(execlists->port) &&
+		   !execlists_is_active(execlists, EXECLISTS_ACTIVE_USER));
+	GEM_BUG_ON(execlists->first && !port_isset(execlists->port));
+
 unlock:
 	spin_unlock_irq(&engine->timeline->lock);