drm/i915: Split out parking from the idle worker for reuse

We will want to park GEM before disengaging the drive^W^W^W unwedging.
Since we already do the work for idling, expose the guts as a new
function that we can then reuse.

v2: Just skip if already parked; makes it more forgiving to use by
future callers.
v3: Extract mark_busy, rename it to i915_gem_unpark and place it next to
i915_gem_park so that we can evaluate it for symmetry more easily.
Calling GEM from inside i915_request looks to be a bit of a layering
violation, for the moment I am imaging them as being notify_cb.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> #v1
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180406155144.27791-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -136,6 +136,100 @@ int i915_mutex_lock_interruptible(struct drm_device *dev)
 	return 0;
 }
 
+static u32 __i915_gem_park(struct drm_i915_private *i915)
+{
+	lockdep_assert_held(&i915->drm.struct_mutex);
+	GEM_BUG_ON(i915->gt.active_requests);
+
+	if (!i915->gt.awake)
+		return I915_EPOCH_INVALID;
+
+	GEM_BUG_ON(i915->gt.epoch == I915_EPOCH_INVALID);
+
+	/*
+	 * Be paranoid and flush a concurrent interrupt to make sure
+	 * we don't reactivate any irq tasklets after parking.
+	 *
+	 * FIXME: Note that even though we have waited for execlists to be idle,
+	 * there may still be an in-flight interrupt even though the CSB
+	 * is now empty. synchronize_irq() makes sure that a residual interrupt
+	 * is completed before we continue, but it doesn't prevent the HW from
+	 * raising a spurious interrupt later. To complete the shield we should
+	 * coordinate disabling the CS irq with flushing the interrupts.
+	 */
+	synchronize_irq(i915->drm.irq);
+
+	intel_engines_park(i915);
+	i915_gem_timelines_park(i915);
+
+	i915_pmu_gt_parked(i915);
+
+	i915->gt.awake = false;
+
+	if (INTEL_GEN(i915) >= 6)
+		gen6_rps_idle(i915);
+
+	intel_display_power_put(i915, POWER_DOMAIN_GT_IRQ);
+
+	intel_runtime_pm_put(i915);
+
+	return i915->gt.epoch;
+}
+
+void i915_gem_park(struct drm_i915_private *i915)
+{
+	lockdep_assert_held(&i915->drm.struct_mutex);
+	GEM_BUG_ON(i915->gt.active_requests);
+
+	if (!i915->gt.awake)
+		return;
+
+	/* Defer the actual call to __i915_gem_park() to prevent ping-pongs */
+	mod_delayed_work(i915->wq, &i915->gt.idle_work, msecs_to_jiffies(100));
+}
+
+void i915_gem_unpark(struct drm_i915_private *i915)
+{
+	lockdep_assert_held(&i915->drm.struct_mutex);
+	GEM_BUG_ON(!i915->gt.active_requests);
+
+	if (i915->gt.awake)
+		return;
+
+	intel_runtime_pm_get_noresume(i915);
+
+	/*
+	 * It seems that the DMC likes to transition between the DC states a lot
+	 * when there are no connected displays (no active power domains) during
+	 * command submission.
+	 *
+	 * This activity has negative impact on the performance of the chip with
+	 * huge latencies observed in the interrupt handler and elsewhere.
+	 *
+	 * Work around it by grabbing a GT IRQ power domain whilst there is any
+	 * GT activity, preventing any DC state transitions.
+	 */
+	intel_display_power_get(i915, POWER_DOMAIN_GT_IRQ);
+
+	i915->gt.awake = true;
+	if (unlikely(++i915->gt.epoch == 0)) /* keep 0 as invalid */
+		i915->gt.epoch = 1;
+
+	intel_enable_gt_powersave(i915);
+	i915_update_gfx_val(i915);
+	if (INTEL_GEN(i915) >= 6)
+		gen6_rps_busy(i915);
+	i915_pmu_gt_unparked(i915);
+
+	intel_engines_unpark(i915);
+
+	i915_queue_hangcheck(i915);
+
+	queue_delayed_work(i915->wq,
+			   &i915->gt.retire_work,
+			   round_jiffies_up_relative(HZ));
+}
+
 int
 i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
 			    struct drm_file *file)
@@ -3496,36 +3590,9 @@ i915_gem_idle_work_handler(struct work_struct *work)
 	if (new_requests_since_last_retire(dev_priv))
 		goto out_unlock;
 
-	/*
-	 * Be paranoid and flush a concurrent interrupt to make sure
-	 * we don't reactivate any irq tasklets after parking.
-	 *
-	 * FIXME: Note that even though we have waited for execlists to be idle,
-	 * there may still be an in-flight interrupt even though the CSB
-	 * is now empty. synchronize_irq() makes sure that a residual interrupt
-	 * is completed before we continue, but it doesn't prevent the HW from
-	 * raising a spurious interrupt later. To complete the shield we should
-	 * coordinate disabling the CS irq with flushing the interrupts.
-	 */
-	synchronize_irq(dev_priv->drm.irq);
-
-	intel_engines_park(dev_priv);
-	i915_gem_timelines_park(dev_priv);
-
-	i915_pmu_gt_parked(dev_priv);
+	epoch = __i915_gem_park(dev_priv);
 
-	GEM_BUG_ON(!dev_priv->gt.awake);
-	dev_priv->gt.awake = false;
-	epoch = dev_priv->gt.epoch;
-	GEM_BUG_ON(epoch == I915_EPOCH_INVALID);
 	rearm_hangcheck = false;
-
-	if (INTEL_GEN(dev_priv) >= 6)
-		gen6_rps_idle(dev_priv);
-
-	intel_display_power_put(dev_priv, POWER_DOMAIN_GT_IRQ);
-
-	intel_runtime_pm_put(dev_priv);
 out_unlock:
 	mutex_unlock(&dev_priv->drm.struct_mutex);
 

drivers/gpu/drm/i915/i915_gem.h

@@ -27,6 +27,8 @@
 
 #include <linux/bug.h>
 
+struct drm_i915_private;
+
 #ifdef CONFIG_DRM_I915_DEBUG_GEM
 #define GEM_BUG_ON(condition) do { if (unlikely((condition))) {	\
 		pr_err("%s:%d GEM_BUG_ON(%s)\n", \
@@ -61,4 +63,7 @@
 
 #define I915_NUM_ENGINES 8
 
+void i915_gem_park(struct drm_i915_private *i915);
+void i915_gem_unpark(struct drm_i915_private *i915);
+
 #endif /* __I915_GEM_H__ */

drivers/gpu/drm/i915/i915_request.c

@@ -255,47 +255,6 @@ int i915_gem_set_global_seqno(struct drm_device *dev, u32 seqno)
 	return reset_all_global_seqno(i915, seqno - 1);
 }
 
-static void mark_busy(struct drm_i915_private *i915)
-{
-	if (i915->gt.awake)
-		return;
-
-	GEM_BUG_ON(!i915->gt.active_requests);
-
-	intel_runtime_pm_get_noresume(i915);
-
-	/*
-	 * It seems that the DMC likes to transition between the DC states a lot
-	 * when there are no connected displays (no active power domains) during
-	 * command submission.
-	 *
-	 * This activity has negative impact on the performance of the chip with
-	 * huge latencies observed in the interrupt handler and elsewhere.
-	 *
-	 * Work around it by grabbing a GT IRQ power domain whilst there is any
-	 * GT activity, preventing any DC state transitions.
-	 */
-	intel_display_power_get(i915, POWER_DOMAIN_GT_IRQ);
-
-	i915->gt.awake = true;
-	if (unlikely(++i915->gt.epoch == 0)) /* keep 0 as invalid */
-		i915->gt.epoch = 1;
-
-	intel_enable_gt_powersave(i915);
-	i915_update_gfx_val(i915);
-	if (INTEL_GEN(i915) >= 6)
-		gen6_rps_busy(i915);
-	i915_pmu_gt_unparked(i915);
-
-	intel_engines_unpark(i915);
-
-	i915_queue_hangcheck(i915);
-
-	queue_delayed_work(i915->wq,
-			   &i915->gt.retire_work,
-			   round_jiffies_up_relative(HZ));
-}
-
 static int reserve_engine(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *i915 = engine->i915;
@@ -313,7 +272,7 @@ static int reserve_engine(struct intel_engine_cs *engine)
 	}
 
 	if (!i915->gt.active_requests++)
-		mark_busy(i915);
+		i915_gem_unpark(i915);
 
 	return 0;
 }
@@ -322,13 +281,8 @@ static void unreserve_engine(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *i915 = engine->i915;
 
-	if (!--i915->gt.active_requests) {
-		/* Cancel the mark_busy() from our reserve_engine() */
-		GEM_BUG_ON(!i915->gt.awake);
-		mod_delayed_work(i915->wq,
-				 &i915->gt.idle_work,
-				 msecs_to_jiffies(100));
-	}
+	if (!--i915->gt.active_requests)
+		i915_gem_park(i915);
 
 	GEM_BUG_ON(!engine->timeline->inflight_seqnos);
 	engine->timeline->inflight_seqnos--;