drm/i915: Use unchecked uncore writes to flush the GTT

As the GTT is outside of the powerwell, we can simplify flushing the
GGTT writes by using an unchecked mmio write and post.

v2: s/unc/uncore/
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190604120022.20472-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -108,22 +108,26 @@
 static int
 i915_get_ggtt_vma_pages(struct i915_vma *vma);
 
-static void gen6_ggtt_invalidate(struct drm_i915_private *dev_priv)
+static void gen6_ggtt_invalidate(struct drm_i915_private *i915)
 {
+	struct intel_uncore *uncore = &i915->uncore;
+
 	/*
 	 * Note that as an uncached mmio write, this will flush the
 	 * WCB of the writes into the GGTT before it triggers the invalidate.
 	 */
-	I915_WRITE(GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
+	intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
 }
 
-static void guc_ggtt_invalidate(struct drm_i915_private *dev_priv)
+static void guc_ggtt_invalidate(struct drm_i915_private *i915)
 {
-	gen6_ggtt_invalidate(dev_priv);
-	I915_WRITE(GEN8_GTCR, GEN8_GTCR_INVALIDATE);
+	struct intel_uncore *uncore = &i915->uncore;
+
+	gen6_ggtt_invalidate(i915);
+	intel_uncore_write_fw(uncore, GEN8_GTCR, GEN8_GTCR_INVALIDATE);
 }
 
-static void gmch_ggtt_invalidate(struct drm_i915_private *dev_priv)
+static void gmch_ggtt_invalidate(struct drm_i915_private *i915)
 {
 	intel_gtt_chipset_flush();
 }
@@ -1347,10 +1351,10 @@ static void gen8_ppgtt_cleanup_4lvl(struct i915_hw_ppgtt *ppgtt)
 
 static void gen8_ppgtt_cleanup(struct i915_address_space *vm)
 {
-	struct drm_i915_private *dev_priv = vm->i915;
+	struct drm_i915_private *i915 = vm->i915;
 	struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
 
-	if (intel_vgpu_active(dev_priv))
+	if (intel_vgpu_active(i915))
 		gen8_ppgtt_notify_vgt(ppgtt, false);
 
 	if (i915_vm_is_4lvl(vm))