drm/i915: Skip switch-to-kernel-context on suspend when wedged

If the HW is already wedged, attempting to submit a request will
generate an -EIO. If we tried this during suspend, we would abort
whereas all we want to do is to go sleep and throw away the corrupt
state.

Fixes: 5ab57c70 ("drm/i915: Flush logical context image out to memory upon suspend")
Testcase: igt/gem_eio/suspend
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171130102951.14965-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -4774,17 +4774,19 @@ int i915_gem_suspend(struct drm_i915_private *dev_priv)
 	 * state. Fortunately, the kernel_context is disposable and we do
 	 * not rely on its state.
 	 */
-	ret = i915_gem_switch_to_kernel_context(dev_priv);
-	if (ret)
-		goto err_unlock;
+	if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
+		ret = i915_gem_switch_to_kernel_context(dev_priv);
+		if (ret)
+			goto err_unlock;
 
-	ret = i915_gem_wait_for_idle(dev_priv,
-				     I915_WAIT_INTERRUPTIBLE |
-				     I915_WAIT_LOCKED);
-	if (ret && ret != -EIO)
-		goto err_unlock;
+		ret = i915_gem_wait_for_idle(dev_priv,
+					     I915_WAIT_INTERRUPTIBLE |
+					     I915_WAIT_LOCKED);
+		if (ret && ret != -EIO)
+			goto err_unlock;
 
-	assert_kernel_context_is_current(dev_priv);
+		assert_kernel_context_is_current(dev_priv);
+	}
 	i915_gem_contexts_lost(dev_priv);
 	mutex_unlock(&dev->struct_mutex);