drm/i915: Introduce DRM_I915_THROTTLE_JIFFIES

As Daniel commented on

commit b7ffe1362c5f468b853223acc9268804aa92afc8
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Apr 27 13:41:24 2015 +0100

    drm/i915: Free RPS boosts for all laggards

it is better to be explicit when sharing hardcoded values such as
throttle/boost timeouts. Make it so!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

3 files changed, 8 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 44d592f3b67c..1038f5c7f15b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -279,6 +279,12 @@ struct drm_i915_file_private {
         struct {
                 spinlock_t lock;
                 struct list_head request_list;
+/* 20ms is a fairly arbitrary limit (greater than the average frame time)
+ * chosen to prevent the CPU getting more than a frame ahead of the GPU
+ * (when using lax throttling for the frontbuffer). We also use it to
+ * offer free GPU waitboosts for severely congested workloads.
+ */
+#define DRM_I915_THROTTLE_JIFFIES msecs_to_jiffies(20)
         } mm;
         struct idr context_idr;
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0ce3e4b3059e..cc206f199d66 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4239,7 +4239,7 @@ i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct drm_i915_file_private *file_priv = file->driver_priv;
-        unsigned long recent_enough = jiffies - msecs_to_jiffies(20);
+        unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES;
         struct drm_i915_gem_request *request, *target = NULL;
         unsigned reset_counter;
         int ret;
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 84809a67fac8..55d993110d51 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4158,7 +4158,7 @@ void gen6_rps_boost(struct drm_i915_private *dev_priv,
         /* Force a RPS boost (and don't count it against the client) if
          * the GPU is severely congested.
          */
-        if (rps && time_after(jiffies, submitted + msecs_to_jiffies(20)))
+        if (rps && time_after(jiffies, submitted + DRM_I915_THROTTLE_JIFFIES))
                 rps = NULL;
 
         mutex_lock(&dev_priv->rps.hw_lock);