drm/i915: Fix RC6 suspend/resume

We restored RC6 twice on resume, even with modesetting off.  Instead,
only restore it once and skip RC6 initialization entirely in non-KMS mode.
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Tested-by: Jeff Chua <jeff.chua.linux@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_drv.h

@@ -307,8 +307,6 @@ typedef struct drm_i915_private {
 	u32 saveDSPACNTR;
 	u32 saveDSPBCNTR;
 	u32 saveDSPARB;
-	u32 saveRENDERSTANDBY;
-	u32 savePWRCTXA;
 	u32 saveHWS;
 	u32 savePIPEACONF;
 	u32 savePIPEBCONF;

drivers/gpu/drm/i915/i915_suspend.c

@@ -732,12 +732,6 @@ int i915_save_state(struct drm_device *dev)
 
 	pci_read_config_byte(dev->pdev, LBB, &dev_priv->saveLBB);
 
-	/* Render Standby */
-	if (I915_HAS_RC6(dev)) {
-		dev_priv->saveRENDERSTANDBY = I915_READ(MCHBAR_RENDER_STANDBY);
-		dev_priv->savePWRCTXA = I915_READ(PWRCTXA);
-	}
-
 	/* Hardware status page */
 	dev_priv->saveHWS = I915_READ(HWS_PGA);
 
@@ -793,12 +787,6 @@ int i915_restore_state(struct drm_device *dev)
 
 	pci_write_config_byte(dev->pdev, LBB, dev_priv->saveLBB);
 
-	/* Render Standby */
-	if (I915_HAS_RC6(dev)) {
-		I915_WRITE(MCHBAR_RENDER_STANDBY, dev_priv->saveRENDERSTANDBY);
-		I915_WRITE(PWRCTXA, dev_priv->savePWRCTXA);
-	}
-
 	/* Hardware status page */
 	I915_WRITE(HWS_PGA, dev_priv->saveHWS);
 

drivers/gpu/drm/i915/intel_display.c

@@ -4593,7 +4593,7 @@ void intel_init_clock_gating(struct drm_device *dev)
 	 * GPU can automatically power down the render unit if given a page
 	 * to save state.
 	 */
-	if (I915_HAS_RC6(dev)) {
+	if (I915_HAS_RC6(dev) && drm_core_check_feature(dev, DRIVER_MODESET)) {
 		struct drm_gem_object *pwrctx;
 		struct drm_i915_gem_object *obj_priv;
 		int ret;