[Intel-gfx] [PATCH 2/2] drm/i915: Expose idle-delays to Kconfig

[Chris Wilson]

We want to expose the parameters for controlling how long it takes for
us to notice and park the GPU after a stream of requests in order to try
 and tune the optimal power-efficiency vs latency of a mostly idle system.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/Kconfig.profile    | 20 ++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem.c         | 12 +++++++++++-
 drivers/gpu/drm/i915/i915_gem_request.c |  2 +-
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
index 8a230eeb98df..02253e7c18e1 100644
--- a/drivers/gpu/drm/i915/Kconfig.profile
+++ b/drivers/gpu/drm/i915/Kconfig.profile
@@ -24,3 +24,23 @@ config DRM_I915_SPIN_REQUEST_CS
 	  spin prior to sleeping again.
 
 	  May be 0 to disable spinning after being woken.
+
+config DRM_I915_GEM_RETIRE_DELAY
+	int
+	default 1000 # milliseconds
+	help
+	  Before parking the engines and the GPU after the final request is
+	  We maintain a background job whose purpose is to keep cleaning up
+	  after userspace, and will be the first to spot an idle system. This
+	  parameter determines th interval between execution of the woker.
+
+config DRM_I915_GEM_PARK_DELAY
+	int
+	default 100 # milliseconds
+	help
+	  Before parking the engines and the GPU after the final request is
+	  retired, we may wait for a small delay to reduce the frequecy of
+	  having to park/unpark and so the latency in executing a new request.
+
+	  May be 0 to immediately start parking the engines after the last
+	  request.
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ba9f67c256f4..ba15f0edda26 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3310,6 +3310,16 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 	return true;
 }
 
+static inline long retire_delay(void)
+{
+	const long delay = msecs_to_jiffies(CONFIG_DRM_I915_GEM_RETIRE_DELAY);
+
+	if (CONFIG_DRM_I915_GEM_RETIRE_DELAY >= 1000)
+		return round_jiffies_up_relative(delay);
+	else
+		return delay;
+}
+
 static void
 i915_gem_retire_work_handler(struct work_struct *work)
 {
@@ -3331,7 +3341,7 @@ i915_gem_retire_work_handler(struct work_struct *work)
 		i915_queue_hangcheck(dev_priv);
 		queue_delayed_work(dev_priv->wq,
 				   &dev_priv->gt.retire_work,
-				   round_jiffies_up_relative(HZ));
+				   retire_delay());
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index bb8b45d4d04d..1c6d7d18e5ee 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -312,7 +312,7 @@ static void unreserve_engine(struct intel_engine_cs *engine)
 		GEM_BUG_ON(!i915->gt.awake);
 		mod_delayed_work(i915->wq,
 				 &i915->gt.idle_work,
-				 msecs_to_jiffies(100));
+				 msecs_to_jiffies(CONFIG_DRM_I915_GEM_PARK_DELAY));
 	}
 
 	GEM_BUG_ON(!engine->timeline->inflight_seqnos);
-- 
2.15.1