drm/i915: Restore very early GPU reset

In commit d03b224f ("drm/i915/gt: Apply sanitiization just before
resume") the GT sanitization was pulled into the resume path as we need
to know the backend in order to do a full reset prior to resume.
However, it is still imperative that we scrub existing GPU state before
clobbering in our early setup, so restore a minimal GPU reset at the
start of our init sequence.

Fixes: d03b224f ("drm/i915/gt: Apply sanitiization just before resume")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191228111255.3086901-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.c

@@ -469,6 +469,12 @@ static void vlv_free_s0ix_state(struct drm_i915_private *i915)
 	i915->vlv_s0ix_state = NULL;
 }
 
+static void sanitize_gpu(struct drm_i915_private *i915)
+{
+	if (!INTEL_INFO(i915)->gpu_reset_clobbers_display)
+		__intel_gt_reset(&i915->gt, ALL_ENGINES);
+}
+
 /**
  * i915_driver_early_probe - setup state not requiring device access
  * @dev_priv: device private
@@ -602,6 +608,9 @@ static int i915_driver_mmio_probe(struct drm_i915_private *dev_priv)
 	if (ret)
 		goto err_uncore;
 
+	/* As early as possible, scrub existing GPU state before clobbering */
+	sanitize_gpu(dev_priv);
+
 	return 0;
 
 err_uncore:
@@ -1817,6 +1826,8 @@ static int i915_drm_resume(struct drm_device *dev)
 
 	disable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
 
+	sanitize_gpu(dev_priv);
+
 	ret = i915_ggtt_enable_hw(dev_priv);
 	if (ret)
 		DRM_ERROR("failed to re-enable GGTT\n");