[Intel-gfx] [PATCH v2] drm/i915/gt: Allow clobbering gpu resets if the display is off

[Chris Wilson]

If the display is inactive, we need not worry about the gpu reset
clobbering the display! To prevent the display changing state between us
checking the active state and doing the hard reset, we introduce the
lightweight reset lock to the atomic commit for the affected (legacy)
platforms.

Testcase: igt/gem_eio/kms
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 11 +++++++++++
 drivers/gpu/drm/i915/gt/intel_reset.c        | 18 +++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 4ee750fa3ef0..a92487d8f4cf 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -13986,6 +13986,7 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
 	struct intel_crtc *crtc;
 	u64 put_domains[I915_MAX_PIPES] = {};
 	intel_wakeref_t wakeref = 0;
+	int srcu;
 	int i;
 
 	intel_atomic_commit_fence_wait(state);
@@ -14005,6 +14006,12 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
 		}
 	}
 
+	/* Prevent starting a GPU reset while we change global display state */
+	srcu = -ENODEV;
+	if (INTEL_INFO(dev_priv)->gpu_reset_clobbers_display)
+		/* only fails if interrupted */
+		srcu = intel_gt_reset_trylock(&dev_priv->gt);
+
 	intel_commit_modeset_disables(state);
 
 	/* FIXME: Eventually get rid of our crtc->config pointer */
@@ -14049,6 +14056,10 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
 	/* Now enable the clocks, plane, pipe, and connectors that we set up. */
 	dev_priv->display.commit_modeset_enables(state);
 
+
+	if (srcu > 0)
+		intel_gt_reset_unlock(&dev_priv->gt, srcu);
+
 	if (state->modeset) {
 		intel_encoders_update_complete(state);
 
diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index d8b1498d7ab7..df4a86bdb6f6 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -7,6 +7,7 @@
 #include <linux/sched/mm.h>
 #include <linux/stop_machine.h>
 
+#include "display/intel_display.h"
 #include "display/intel_display_types.h"
 #include "display/intel_overlay.h"
 
@@ -729,6 +730,21 @@ static void nop_submit_request(struct i915_request *request)
 	intel_engine_queue_breadcrumbs(engine);
 }
 
+static bool reset_clobbers_display(struct drm_i915_private *i915)
+{
+	struct intel_crtc *crtc;
+
+	if (!INTEL_INFO(i915)->gpu_reset_clobbers_display)
+		return false;
+
+	for_each_intel_crtc(&i915->drm, crtc) {
+		if (crtc->active)
+			return true;
+	}
+
+	return false;
+}
+
 static void __intel_gt_set_wedged(struct intel_gt *gt)
 {
 	struct intel_engine_cs *engine;
@@ -755,7 +771,7 @@ static void __intel_gt_set_wedged(struct intel_gt *gt)
 	awake = reset_prepare(gt);
 
 	/* Even if the GPU reset fails, it should still stop the engines */
-	if (!INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
+	if (!reset_clobbers_display(gt->i915))
 		__intel_gt_reset(gt, ALL_ENGINES);
 
 	for_each_engine(engine, gt->i915, id)
-- 
2.23.0