drm/i915: Skip force-wake for uncached mmio flush of GGTT writes

The trick of using an uncached mmio read to ensure that the GGTT writes
are flushed does not require us to do the forcewake dance, so avoid it
in the hope of reducing the frequency that we do keep the device forced
awake.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170318104257.694-1-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 58e1db77d70e9cc3ebfc652d39efe85b665e637e..bb65072f688d15c5b769b1406c97f1f4d36d6929 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3307,8 +3307,11 @@ i915_gem_object_flush_gtt_write_domain(struct drm_i915_gem_object *obj)
         * system agents we cannot reproduce this behaviour).
         */
        wmb();
-       if (INTEL_GEN(dev_priv) >= 6 && !HAS_LLC(dev_priv))
-               POSTING_READ(RING_ACTHD(dev_priv->engine[RCS]->mmio_base));
+       if (INTEL_GEN(dev_priv) >= 6 && !HAS_LLC(dev_priv)) {
+               spin_lock_irq(&dev_priv->uncore.lock);
+               POSTING_READ_FW(RING_ACTHD(dev_priv->engine[RCS]->mmio_base));
+               spin_unlock_irq(&dev_priv->uncore.lock);
+       }
 
        intel_fb_obj_flush(obj, write_origin(obj, I915_GEM_DOMAIN_GTT));