drm/i915: Enable irq to trace batch buffer completion.

If we trigger a tracepoint for batch buffer submission, it is a reasonable
assumption that we wish to also trace the batch buffer completion. So in
order to capture the completion events, we need to enable irqs... However,
we cannot rely on the completion event to disable the irq later, so we
defer the irq disable to the retire request.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_dma.c

@@ -1468,6 +1468,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	spin_lock_init(&dev_priv->user_irq_lock);
 	spin_lock_init(&dev_priv->error_lock);
 	dev_priv->user_irq_refcount = 0;
+	dev_priv->trace_irq_seqno = 0;
 
 	ret = drm_vblank_init(dev, I915_NUM_PIPE);
 

drivers/gpu/drm/i915/i915_drv.h

@@ -202,6 +202,7 @@ typedef struct drm_i915_private {
 	spinlock_t user_irq_lock;
 	/** Refcount for i915_user_irq_get() versus i915_user_irq_put(). */
 	int user_irq_refcount;
+	u32 trace_irq_seqno;
 	/** Cached value of IMR to avoid reads in updating the bitfield */
 	u32 irq_mask_reg;
 	u32 pipestat[2];
@@ -665,6 +666,7 @@ extern int i915_irq_emit(struct drm_device *dev, void *data,
 extern int i915_irq_wait(struct drm_device *dev, void *data,
 			 struct drm_file *file_priv);
 void i915_user_irq_get(struct drm_device *dev);
+void i915_trace_irq_get(struct drm_device *dev, u32 seqno);
 void i915_user_irq_put(struct drm_device *dev);
 extern void i915_enable_interrupt (struct drm_device *dev);
 

drivers/gpu/drm/i915/i915_gem.c

@@ -1770,7 +1770,7 @@ i915_gem_retire_requests(struct drm_device *dev)
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	uint32_t seqno;
 
-	if (!dev_priv->hw_status_page)
+	if (!dev_priv->hw_status_page || list_empty(&dev_priv->mm.request_list))
 		return;
 
 	seqno = i915_get_gem_seqno(dev);
@@ -1794,6 +1794,12 @@ i915_gem_retire_requests(struct drm_device *dev)
 		} else
 			break;
 	}
+
+	if (unlikely (dev_priv->trace_irq_seqno &&
+		      i915_seqno_passed(dev_priv->trace_irq_seqno, seqno))) {
+		i915_user_irq_put(dev);
+		dev_priv->trace_irq_seqno = 0;
+	}
 }
 
 void

drivers/gpu/drm/i915/i915_irq.c

@@ -725,6 +725,16 @@ void i915_user_irq_put(struct drm_device *dev)
 	spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 }
 
+void i915_trace_irq_get(struct drm_device *dev, u32 seqno)
+{
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+
+	if (dev_priv->trace_irq_seqno == 0)
+		i915_user_irq_get(dev);
+
+	dev_priv->trace_irq_seqno = seqno;
+}
+
 static int i915_wait_irq(struct drm_device * dev, int irq_nr)
 {
 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;

drivers/gpu/drm/i915/i915_trace.h

@@ -165,6 +165,7 @@ TRACE_EVENT(i915_gem_request_submit,
 	    TP_fast_assign(
 			   __entry->dev = dev->primary->index;
 			   __entry->seqno = seqno;
+			   i915_trace_irq_get(dev, seqno);
 			   ),
 
 	    TP_printk("dev=%u, seqno=%u", __entry->dev, __entry->seqno)