drm/i915: Always wake the device to flush the GTT

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@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170829192546.1087-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 44a7cb0e8badb71037d841466f12f3c6470bd171..e4cc08bc518cc107f6b77e3ef716d499c4d4058f 100644 (file)
--- 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,