[Intel-gfx] [PATCH] drm/i915: Always wake the device to flush the GTT

[Chris Wilson]

Since we hold the device wakeref when writing through the GTT (otherwise
the writes would fail), we presumed that before the device sleeps those
writes would naturally be flushed and that we wouldn't need our mmio
read trick. However, that presumption seems false and a sleepy bxt seems
to require us to always manually flush the GTT writes prior to direct
access.

Fixes: e2a2aa36a509 ("drm/i915: Check we have an wake device before flushing GTT writes")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 43834dee4e8d..890fe2802973 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -695,12 +695,11 @@ flush_write_domain(struct drm_i915_gem_object *obj, unsigned int flush_domains)
 	switch (obj->base.write_domain) {
 	case I915_GEM_DOMAIN_GTT:
 		if (INTEL_GEN(dev_priv) >= 6 && !HAS_LLC(dev_priv)) {
-			if (intel_runtime_pm_get_if_in_use(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_runtime_pm_put(dev_priv);
-			}
+			intel_runtime_pm_get(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_runtime_pm_put(dev_priv);
 		}
 
 		intel_fb_obj_flush(obj,
-- 
2.14.1