drm/i915: Use spinlocks for checking when to waitboost

In commit 1854d5ca0dd7a9fc11243ff220a3e93fce2b4d3e
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Tue Apr 7 16:20:32 2015 +0100

    drm/i915: Deminish contribution of wait-boosting from clients

we removed an atomic timer based check for allowing waitboosting and
moved it below the mutex taken during RPS. However, that mutex can be
held for long periods of time on Vallyview/Cherryview as communication
with the PCU is slow. As clients may frequently wait for results (e.g.
such as tranform feedback) we introduced contention between the client
and the RPS worker. We can take advantage of the RPS worker, by
switching the wait boost decision to use spin locks and defer the
actual reclocking to the worker.

Fixes a regression of up to 45% on Baytrail and Baswell!

v2 (Daniel):
- Use max_freq_softlimit instead of the not-yet-merged boost
  frequency.
- Don't inject a fake irq into the boost work, instead treat
  client_boost as just another legit waker.

v3: Drop the now unused mask (Chris).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90112
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 3 insertions, 14 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index fece922718e2..88cc793c46d3 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2300,15 +2300,6 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
 	struct drm_device *dev = node->minor->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_file *file;
-	int ret;
-
-	ret = mutex_lock_interruptible(&dev->struct_mutex);
-	if (ret)
-		return ret;
-
-	ret = mutex_lock_interruptible(&dev_priv->rps.hw_lock);
-	if (ret)
-		goto unlock;
 
 	seq_printf(m, "RPS enabled? %d\n", dev_priv->rps.enabled);
 	seq_printf(m, "GPU busy? %d\n", dev_priv->mm.busy);
@@ -2319,6 +2310,7 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
 		   intel_gpu_freq(dev_priv, dev_priv->rps.min_freq_softlimit),
 		   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq_softlimit),
 		   intel_gpu_freq(dev_priv, dev_priv->rps.max_freq));
+	spin_lock(&dev_priv->rps.client_lock);
 	list_for_each_entry_reverse(file, &dev->filelist, lhead) {
 		struct drm_i915_file_private *file_priv = file->driver_priv;
 		struct task_struct *task;
@@ -2339,12 +2331,9 @@ static int i915_rps_boost_info(struct seq_file *m, void *data)
 		   dev_priv->rps.mmioflips.boosts,
 		   list_empty(&dev_priv->rps.mmioflips.link) ? "" : ", active");
 	seq_printf(m, "Kernel boosts: %d\n", dev_priv->rps.boosts);
+	spin_unlock(&dev_priv->rps.client_lock);
 
-	mutex_unlock(&dev_priv->rps.hw_lock);
-unlock:
-	mutex_unlock(&dev->struct_mutex);
-
-	return ret;
+	return 0;
 }
 
 static int i915_llc(struct seq_file *m, void *data)