drm/i915: Avoid concurrent access when marking the device as idle/busy

As suggested by Daniel, rip out the independent timers for device and
crtc busyness and integrate the manual powermanagement of the display
engine into the GEM core and its request tracking. The benefits are that
the code is a lot smaller, fewer moving parts and should fit more neatly
into the overall activity tracking of the driver.

v2: Complete overhaul and removal of the racy timers and workers.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -785,9 +785,6 @@ typedef struct drm_i915_private {
 	bool lvds_downclock_avail;
 	/* indicates the reduced downclock for LVDS*/
 	int lvds_downclock;
-	struct work_struct idle_work;
-	struct timer_list idle_timer;
-	bool busy;
 	u16 orig_clock;
 	int child_dev_num;
 	struct child_device_config *child_dev;

drivers/gpu/drm/i915/i915_gem.c

@@ -1462,11 +1462,14 @@ i915_gem_object_move_to_inactive(struct drm_i915_gem_object *obj)
 	struct drm_device *dev = obj->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	list_move_tail(&obj->mm_list, &dev_priv->mm.inactive_list);
-
 	BUG_ON(obj->base.write_domain & ~I915_GEM_GPU_DOMAINS);
 	BUG_ON(!obj->active);
 
+	if (obj->pin_count) /* are we a framebuffer? */
+		intel_mark_fb_idle(obj);
+
+	list_move_tail(&obj->mm_list, &dev_priv->mm.inactive_list);
+
 	list_del_init(&obj->ring_list);
 	obj->ring = NULL;
 
@@ -1602,9 +1605,11 @@ i915_add_request(struct intel_ring_buffer *ring,
 				  jiffies +
 				  msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
 		}
-		if (was_empty)
+		if (was_empty) {
 			queue_delayed_work(dev_priv->wq,
 					   &dev_priv->mm.retire_work, HZ);
+			intel_mark_busy(dev_priv->dev);
+		}
 	}
 
 	return 0;
@@ -1810,6 +1815,8 @@ i915_gem_retire_work_handler(struct work_struct *work)
 
 	if (!dev_priv->mm.suspended && !idle)
 		queue_delayed_work(dev_priv->wq, &dev_priv->mm.retire_work, HZ);
+	if (idle)
+		intel_mark_idle(dev);
 
 	mutex_unlock(&dev->struct_mutex);
 }

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -767,13 +767,11 @@ i915_gem_execbuffer_move_to_active(struct list_head *objects,
 			obj->dirty = 1;
 			obj->last_write_seqno = seqno;
 			if (obj->pin_count) /* check for potential scanout */
-				intel_mark_busy(ring->dev, obj);
+				intel_mark_fb_busy(obj);
 		}
 
 		trace_i915_gem_object_change_domain(obj, old_read, old_write);
 	}
-
-	intel_mark_busy(ring->dev, NULL);
 }
 
 static void

drivers/gpu/drm/i915/intel_display.c

@@ -5860,46 +5860,6 @@ struct drm_display_mode *intel_crtc_mode_get(struct drm_device *dev,
 	return mode;
 }
 
-#define GPU_IDLE_TIMEOUT 500 /* ms */
-
-/* When this timer fires, we've been idle for awhile */
-static void intel_gpu_idle_timer(unsigned long arg)
-{
-	struct drm_device *dev = (struct drm_device *)arg;
-	drm_i915_private_t *dev_priv = dev->dev_private;
-
-	if (!list_empty(&dev_priv->mm.active_list)) {
-		/* Still processing requests, so just re-arm the timer. */
-		mod_timer(&dev_priv->idle_timer, jiffies +
-			  msecs_to_jiffies(GPU_IDLE_TIMEOUT));
-		return;
-	}
-
-	dev_priv->busy = false;
-	queue_work(dev_priv->wq, &dev_priv->idle_work);
-}
-
-#define CRTC_IDLE_TIMEOUT 1000 /* ms */
-
-static void intel_crtc_idle_timer(unsigned long arg)
-{
-	struct intel_crtc *intel_crtc = (struct intel_crtc *)arg;
-	struct drm_crtc *crtc = &intel_crtc->base;
-	drm_i915_private_t *dev_priv = crtc->dev->dev_private;
-	struct intel_framebuffer *intel_fb;
-
-	intel_fb = to_intel_framebuffer(crtc->fb);
-	if (intel_fb && intel_fb->obj->active) {
-		/* The framebuffer is still being accessed by the GPU. */
-		mod_timer(&intel_crtc->idle_timer, jiffies +
-			  msecs_to_jiffies(CRTC_IDLE_TIMEOUT));
-		return;
-	}
-
-	intel_crtc->busy = false;
-	queue_work(dev_priv->wq, &dev_priv->idle_work);
-}
-
 static void intel_increase_pllclock(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
@@ -5929,10 +5889,6 @@ static void intel_increase_pllclock(struct drm_crtc *crtc)
 		if (dpll & DISPLAY_RATE_SELECT_FPA1)
 			DRM_DEBUG_DRIVER("failed to upclock LVDS!\n");
 	}
-
-	/* Schedule downclock */
-	mod_timer(&intel_crtc->idle_timer, jiffies +
-		  msecs_to_jiffies(CRTC_IDLE_TIMEOUT));
 }
 
 static void intel_decrease_pllclock(struct drm_crtc *crtc)
@@ -5971,89 +5927,48 @@ static void intel_decrease_pllclock(struct drm_crtc *crtc)
 
 }
 
-/**
- * intel_idle_update - adjust clocks for idleness
- * @work: work struct
- *
- * Either the GPU or display (or both) went idle.  Check the busy status
- * here and adjust the CRTC and GPU clocks as necessary.
- */
-static void intel_idle_update(struct work_struct *work)
+void intel_mark_busy(struct drm_device *dev)
+{
+	intel_sanitize_pm(dev);
+	i915_update_gfx_val(dev->dev_private);
+}
+
+void intel_mark_idle(struct drm_device *dev)
 {
-	drm_i915_private_t *dev_priv = container_of(work, drm_i915_private_t,
-						    idle_work);
-	struct drm_device *dev = dev_priv->dev;
+	intel_sanitize_pm(dev);
+}
+
+void intel_mark_fb_busy(struct drm_i915_gem_object *obj)
+{
+	struct drm_device *dev = obj->base.dev;
 	struct drm_crtc *crtc;
-	struct intel_crtc *intel_crtc;
 
 	if (!i915_powersave)
 		return;
 
-	mutex_lock(&dev->struct_mutex);
-
-	i915_update_gfx_val(dev_priv);
-
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
-		/* Skip inactive CRTCs */
 		if (!crtc->fb)
 			continue;
 
-		intel_crtc = to_intel_crtc(crtc);
-		if (!intel_crtc->busy)
-			intel_decrease_pllclock(crtc);
+		if (to_intel_framebuffer(crtc->fb)->obj == obj)
+			intel_increase_pllclock(crtc);
 	}
-
-
-	mutex_unlock(&dev->struct_mutex);
 }
 
-/**
- * intel_mark_busy - mark the GPU and possibly the display busy
- * @dev: drm device
- * @obj: object we're operating on
- *
- * Callers can use this function to indicate that the GPU is busy processing
- * commands.  If @obj matches one of the CRTC objects (i.e. it's a scanout
- * buffer), we'll also mark the display as busy, so we know to increase its
- * clock frequency.
- */
-void intel_mark_busy(struct drm_device *dev, struct drm_i915_gem_object *obj)
+void intel_mark_fb_idle(struct drm_i915_gem_object *obj)
 {
-	drm_i915_private_t *dev_priv = dev->dev_private;
-	struct drm_crtc *crtc = NULL;
-	struct intel_framebuffer *intel_fb;
-	struct intel_crtc *intel_crtc;
-
-	if (!drm_core_check_feature(dev, DRIVER_MODESET))
-		return;
-
-	if (!dev_priv->busy) {
-		intel_sanitize_pm(dev);
-		dev_priv->busy = true;
-	} else
-		mod_timer(&dev_priv->idle_timer, jiffies +
-			  msecs_to_jiffies(GPU_IDLE_TIMEOUT));
+	struct drm_device *dev = obj->base.dev;
+	struct drm_crtc *crtc;
 
-	if (obj == NULL)
+	if (!i915_powersave)
 		return;
 
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
 		if (!crtc->fb)
 			continue;
 
-		intel_crtc = to_intel_crtc(crtc);
-		intel_fb = to_intel_framebuffer(crtc->fb);
-		if (intel_fb->obj == obj) {
-			if (!intel_crtc->busy) {
-				/* Non-busy -> busy, upclock */
-				intel_increase_pllclock(crtc);
-				intel_crtc->busy = true;
-			} else {
-				/* Busy -> busy, put off timer */
-				mod_timer(&intel_crtc->idle_timer, jiffies +
-					  msecs_to_jiffies(CRTC_IDLE_TIMEOUT));
-			}
-		}
+		if (to_intel_framebuffer(crtc->fb)->obj == obj)
+			intel_decrease_pllclock(crtc);
 	}
 }
 
@@ -6512,7 +6427,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 		goto cleanup_pending;
 
 	intel_disable_fbc(dev);
-	intel_mark_busy(dev, obj);
+	intel_mark_fb_busy(obj);
 	mutex_unlock(&dev->struct_mutex);
 
 	trace_i915_flip_request(intel_crtc->plane, obj);
@@ -6678,11 +6593,6 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
 	}
 
 	drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
-
-	intel_crtc->busy = false;
-
-	setup_timer(&intel_crtc->idle_timer, intel_crtc_idle_timer,
-		    (unsigned long)intel_crtc);
 }
 
 int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,
@@ -7265,10 +7175,6 @@ void intel_modeset_init(struct drm_device *dev)
 	/* Just disable it once at startup */
 	i915_disable_vga(dev);
 	intel_setup_outputs(dev);
-
-	INIT_WORK(&dev_priv->idle_work, intel_idle_update);
-	setup_timer(&dev_priv->idle_timer, intel_gpu_idle_timer,
-		    (unsigned long)dev);
 }
 
 void intel_modeset_gem_init(struct drm_device *dev)
@@ -7319,14 +7225,6 @@ void intel_modeset_cleanup(struct drm_device *dev)
 	/* flush any delayed tasks or pending work */
 	flush_scheduled_work();
 
-	/* Shut off idle work before the crtcs get freed. */
-	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
-		intel_crtc = to_intel_crtc(crtc);
-		del_timer_sync(&intel_crtc->idle_timer);
-	}
-	del_timer_sync(&dev_priv->idle_timer);
-	cancel_work_sync(&dev_priv->idle_work);
-
 	drm_mode_config_cleanup(dev);
 }
 

drivers/gpu/drm/i915/intel_drv.h

@@ -156,8 +156,6 @@ struct intel_crtc {
 	int dpms_mode;
 	bool active; /* is the crtc on? independent of the dpms mode */
 	bool primary_disabled; /* is the crtc obscured by a plane? */
-	bool busy; /* is scanout buffer being updated frequently? */
-	struct timer_list idle_timer;
 	bool lowfreq_avail;
 	struct intel_overlay *overlay;
 	struct intel_unpin_work *unpin_work;
@@ -373,8 +371,10 @@ extern bool intel_sdvo_init(struct drm_device *dev, uint32_t sdvo_reg,
 			    bool is_sdvob);
 extern void intel_dvo_init(struct drm_device *dev);
 extern void intel_tv_init(struct drm_device *dev);
-extern void intel_mark_busy(struct drm_device *dev,
-			    struct drm_i915_gem_object *obj);
+extern void intel_mark_busy(struct drm_device *dev);
+extern void intel_mark_idle(struct drm_device *dev);
+extern void intel_mark_fb_busy(struct drm_i915_gem_object *obj);
+extern void intel_mark_fb_idle(struct drm_i915_gem_object *obj);
 extern bool intel_lvds_init(struct drm_device *dev);
 extern void intel_dp_init(struct drm_device *dev, int output_reg,
 			  enum port port);

drivers/gpu/drm/i915/intel_pm.c

@@ -3075,14 +3075,17 @@ EXPORT_SYMBOL_GPL(i915_gpu_lower);
 bool i915_gpu_busy(void)
 {
 	struct drm_i915_private *dev_priv;
+	struct intel_ring_buffer *ring;
 	bool ret = false;
+	int i;
 
 	spin_lock(&mchdev_lock);
 	if (!i915_mch_dev)
 		goto out_unlock;
 	dev_priv = i915_mch_dev;
 
-	ret = dev_priv->busy;
+	for_each_ring(ring, dev_priv, i)
+		ret |= !list_empty(&ring->request_list);
 
 out_unlock:
 	spin_unlock(&mchdev_lock);