[PATCH 21/22] HACK: drm/i915: Make non-blocking GPU synchronization optional

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Add a module parameter that allows one to easily change between blocking
and non-blocking GPU synchronization with atomic page flips.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_stub.c          |    5 +++++
 drivers/gpu/drm/i915/intel_atomic.c |   10 +++++++++-
 2 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index c236fd2..52d5750 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -46,16 +46,21 @@ EXPORT_SYMBOL(drm_vblank_offdelay);
 unsigned int drm_timestamp_precision = 20;  /* Default to 20 usecs. */
 EXPORT_SYMBOL(drm_timestamp_precision);
 
+unsigned int drm_async_gpu = 0;	/* 1 to enable async gpu wait */
+EXPORT_SYMBOL(drm_async_gpu);
+
 MODULE_AUTHOR(CORE_AUTHOR);
 MODULE_DESCRIPTION(CORE_DESC);
 MODULE_LICENSE("GPL and additional rights");
 MODULE_PARM_DESC(debug, "Enable debug output");
 MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs]");
 MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");
+MODULE_PARM_DESC(async_gpu, "Async GPU wait");
 
 module_param_named(debug, drm_debug, int, 0600);
 module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);
 module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);
+module_param_named(async_gpu, drm_async_gpu, int, 0600);
 
 struct idr drm_minors_idr;
 
diff --git a/drivers/gpu/drm/i915/intel_atomic.c b/drivers/gpu/drm/i915/intel_atomic.c
index bfa6da6..d3aa566 100644
--- a/drivers/gpu/drm/i915/intel_atomic.c
+++ b/drivers/gpu/drm/i915/intel_atomic.c
@@ -801,11 +801,13 @@ static void unpin_fbs(struct drm_device *dev,
 	}
 }
 
+extern unsigned int drm_async_gpu;
+
 static int pin_fbs(struct drm_device *dev,
 		   struct intel_atomic_state *s)
 {
 	int i, ret;
-	bool nonblock = s->flags & DRM_MODE_ATOMIC_NONBLOCK;
+	bool nonblock = drm_async_gpu && (s->flags & DRM_MODE_ATOMIC_NONBLOCK);
 
 	for (i = 0; i < dev->mode_config.num_crtc; i++) {
 		struct intel_crtc_state *st = &s->crtc[i];
@@ -2359,6 +2361,12 @@ static void atomic_pipe_commit(struct drm_device *dev,
 	if (list_empty(&flips))
 		return;
 
+	if (!drm_async_gpu) {
+		struct intel_crtc *intel_crtc = to_intel_crtc(intel_get_crtc_for_pipe(dev, pipe));
+		intel_atomic_schedule_flips(dev_priv, intel_crtc, &flips);
+		return;
+	}
+
 	spin_lock_irqsave(&dev_priv->flip.lock, flags);
 	list_for_each_entry_safe(intel_flip, next, &flips, base.list)
 		intel_atomic_postpone_flip(dev, intel_flip);
-- 
1.7.8.6