drm/i915: Reduce hangcheck frequency

By reducing the hangcheck frequency we check less often, conserving
resources, and still detect a lock up quickly. On a fast machine with a
slow GPU (like a Core2 paired with a 945G) it is easy for the hangcheck to
misfire as we check too fast.

Also once hung and if we fail to completely reset the chip, we have a
nasty habit of proclaming a hang many times a second and generating a
strobe-like display.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.h

@@ -299,7 +299,7 @@ typedef struct drm_i915_private {
 	int num_pipe;
 
 	/* For hangcheck timer */
-#define DRM_I915_HANGCHECK_PERIOD 75 /* in jiffies */
+#define DRM_I915_HANGCHECK_PERIOD 250 /* in ms */
 	struct timer_list hangcheck_timer;
 	int hangcheck_count;
 	uint32_t last_acthd;

drivers/gpu/drm/i915/i915_gem.c

@@ -1639,9 +1639,11 @@ i915_add_request(struct drm_device *dev,
 	}
 
 	if (!dev_priv->mm.suspended) {
-		mod_timer(&dev_priv->hangcheck_timer, jiffies + DRM_I915_HANGCHECK_PERIOD);
+		mod_timer(&dev_priv->hangcheck_timer,
+			  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
 		if (was_empty)
-			queue_delayed_work(dev_priv->wq, &dev_priv->mm.retire_work, HZ);
+			queue_delayed_work(dev_priv->wq,
+					   &dev_priv->mm.retire_work, HZ);
 	}
 	return seqno;
 }

drivers/gpu/drm/i915/i915_irq.c

@@ -328,7 +328,8 @@ static irqreturn_t ironlake_irq_handler(struct drm_device *dev)
 		trace_i915_gem_request_complete(dev, seqno);
 		DRM_WAKEUP(&dev_priv->render_ring.irq_queue);
 		dev_priv->hangcheck_count = 0;
-		mod_timer(&dev_priv->hangcheck_timer, jiffies + DRM_I915_HANGCHECK_PERIOD);
+		mod_timer(&dev_priv->hangcheck_timer,
+			  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
 	}
 	if (gt_iir & GT_BSD_USER_INTERRUPT)
 		DRM_WAKEUP(&dev_priv->bsd_ring.irq_queue);
@@ -1018,7 +1019,8 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 			trace_i915_gem_request_complete(dev, seqno);
 			DRM_WAKEUP(&dev_priv->render_ring.irq_queue);
 			dev_priv->hangcheck_count = 0;
-			mod_timer(&dev_priv->hangcheck_timer, jiffies + DRM_I915_HANGCHECK_PERIOD);
+			mod_timer(&dev_priv->hangcheck_timer,
+				  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
 		}
 
 		if (HAS_BSD(dev) && (iir & I915_BSD_USER_INTERRUPT))
@@ -1394,7 +1396,8 @@ void i915_hangcheck_elapsed(unsigned long data)
 
 out:
 	/* Reset timer case chip hangs without another request being added */
-	mod_timer(&dev_priv->hangcheck_timer, jiffies + DRM_I915_HANGCHECK_PERIOD);
+	mod_timer(&dev_priv->hangcheck_timer,
+		  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
 }
 
 /* drm_dma.h hooks