drm/i915: Accurately track when we mark the hardware as idle/busy

We currently call intel_mark_idle() too often, as we do so as a
side-effect of processing the request queue. However, we the calls to
intel_mark_idle() are expected to be paired with a call to
intel_mark_busy() (or else we try to idle the hardware by accessing
registers that are already disabled). Make the idle/busy tracking
explicit to prevent the multiple calls.

v2: We can drop some of the complexity in __i915_add_request() as
queue_delayed_work() already behaves as we want (not requeuing the item
if it is already in the queue) and mark_busy/mark_idle imply that the
idle task is inactive.

v3: We do still need to cancel the pending idle task so that it is sent
again after the current busy load completes (not in the middle of it).

Reported-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 944c617..0d1e8be 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1124,6 +1124,14 @@ struct i915_gem_mm {
         */
        bool interruptible;
 
+       /**
+        * Is the GPU currently considered idle, or busy executing userspace
+        * requests?  Whilst idle, we attempt to power down the hardware and
+        * display clocks. In order to reduce the effect on performance, there
+        * is a slight delay before we do so.
+        */
+       bool busy;
+
        /** Bit 6 swizzling required for X tiling */
        uint32_t bit_6_swizzle_x;
        /** Bit 6 swizzling required for Y tiling */

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 3618bb0..6978e69 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2148,7 +2148,6 @@ int __i915_add_request(struct intel_ring_buffer *ring,
        drm_i915_private_t *dev_priv = ring->dev->dev_private;
        struct drm_i915_gem_request *request;
        u32 request_ring_position, request_start;
-       int was_empty;
        int ret;
 
        request_start = intel_ring_get_tail(ring);
@@ -2199,7 +2198,6 @@ int __i915_add_request(struct intel_ring_buffer *ring,
                i915_gem_context_reference(request->ctx);
 
        request->emitted_jiffies = jiffies;
-       was_empty = list_empty(&ring->request_list);
        list_add_tail(&request->list, &ring->request_list);
        request->file_priv = NULL;
 
@@ -2220,13 +2218,11 @@ int __i915_add_request(struct intel_ring_buffer *ring,
        if (!dev_priv->ums.mm_suspended) {
                i915_queue_hangcheck(ring->dev);
 
-               if (was_empty) {
-                       cancel_delayed_work_sync(&dev_priv->mm.idle_work);
-                       queue_delayed_work(dev_priv->wq,
-                                          &dev_priv->mm.retire_work,
-                                          round_jiffies_up_relative(HZ));
-                       intel_mark_busy(dev_priv->dev);
-               }
+               cancel_delayed_work_sync(&dev_priv->mm.idle_work);
+               queue_delayed_work(dev_priv->wq,
+                                  &dev_priv->mm.retire_work,
+                                  round_jiffies_up_relative(HZ));
+               intel_mark_busy(dev_priv->dev);
        }
 
        if (out_seqno)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 842b07e..ef26312 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8197,8 +8197,12 @@ void intel_mark_busy(struct drm_device *dev)
 {
        struct drm_i915_private *dev_priv = dev->dev_private;
 
+       if (dev_priv->mm.busy)
+               return;
+
        hsw_package_c8_gpu_busy(dev_priv);
        i915_update_gfx_val(dev_priv);
+       dev_priv->mm.busy = true;
 }
 
 void intel_mark_idle(struct drm_device *dev)
@@ -8206,6 +8210,11 @@ void intel_mark_idle(struct drm_device *dev)
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct drm_crtc *crtc;
 
+       if (!dev_priv->mm.busy)
+               return;
+
+       dev_priv->mm.busy = false;
+
        hsw_package_c8_gpu_idle(dev_priv);
 
        if (!i915.powersave)