[Intel-gfx] [PATCH] drm/i915: Restore the kernel context after a GPU reset on an idle engine

[Chris Wilson]

As part of the system requirement for powersaving is that we always have
a context loaded. Upon boot and resume, we load the kernel_context to
ensure that some valid state is set before powersaving kicks in, we
should do so after a full GPU reset as well. We only need to do so for
an idle engine, as any active engines will restart by executing the
stuck request, loading its context, for the idle engine we create a
new request to load the kernel_context instead.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4a7f5579a7a5..189725a8fed6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3119,6 +3119,15 @@ void i915_gem_reset(struct drm_i915_private *dev_priv)
 		ctx = fetch_and_zero(&engine->last_retired_context);
 		if (ctx)
 			engine->context_unpin(engine, ctx);
+
+		if (list_empty(&engine->timeline->requests)) {
+			struct drm_i915_gem_request *rq;
+
+			rq = i915_gem_request_alloc(engine,
+						    dev_priv->kernel_context);
+			if (!IS_ERR(rq))
+				__i915_add_request(rq, false);
+		}
 	}
 
 	i915_gem_restore_fences(dev_priv);
-- 
2.15.1