drm/i915: Only enable IPS polling for gen5

On SandyBridge IPS was entirely implemented in hardware and not reliant
on the driver monitoring power consumption and feeding back desired run
states, so the hardware is able to adapt quicker and more flexibly. Which
is a huge relief for us as we no longer have to carry empirically
derived magic algorithms.

Yet despite the advance in technology, the driver was still doing its
IPS polling on all machines. Restrict it to the only supported hardware,
Clarkdale/Arrandale.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1193,6 +1193,9 @@ static int i915_emon_status(struct seq_file *m, void *unused)
 	unsigned long temp, chipset, gfx;
 	int ret;
 
+	if (!IS_GEN5(dev))
+		return -ENODEV;
+
 	ret = mutex_lock_interruptible(&dev->struct_mutex);
 	if (ret)
 		return ret;

drivers/gpu/drm/i915/i915_dma.c

@@ -1520,6 +1520,9 @@ void i915_update_gfx_val(struct drm_i915_private *dev_priv)
 	unsigned long diffms;
 	u32 count;
 
+	if (dev_priv->info->gen != 5)
+		return;
+
 	getrawmonotonic(&now);
 	diff1 = timespec_sub(now, dev_priv->last_time2);
 
@@ -1959,12 +1962,14 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	setup_timer(&dev_priv->hangcheck_timer, i915_hangcheck_elapsed,
 		    (unsigned long) dev);
 
-	spin_lock(&mchdev_lock);
-	i915_mch_dev = dev_priv;
-	dev_priv->mchdev_lock = &mchdev_lock;
-	spin_unlock(&mchdev_lock);
+	if (IS_GEN5(dev)) {
+		spin_lock(&mchdev_lock);
+		i915_mch_dev = dev_priv;
+		dev_priv->mchdev_lock = &mchdev_lock;
+		spin_unlock(&mchdev_lock);
 
-	ips_ping_for_i915_load();
+		ips_ping_for_i915_load();
+	}
 
 	return 0;