i915: Save/restore MCHBAR_RENDER_STANDBY on GM965/GM45

This register is set by the 2D driver to prevent lockups, and so it needs to
be preserved across suspend/resume too. This makes my X200s work.
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/gpu/drm/i915/i915_drv.h

@@ -157,6 +157,7 @@ typedef struct drm_i915_private {
 	u32 saveDSPACNTR;
 	u32 saveDSPBCNTR;
 	u32 saveDSPARB;
+	u32 saveRENDERSTANDBY;
 	u32 savePIPEACONF;
 	u32 savePIPEBCONF;
 	u32 savePIPEASRC;

drivers/gpu/drm/i915/i915_reg.h

@@ -527,6 +527,9 @@
 #define C0DRB3			0x10206
 #define C1DRB3			0x10606
 
+/** GM965 GM45 render standby register */
+#define MCHBAR_RENDER_STANDBY	0x111B8
+
 /*
  * Overlay regs
  */

drivers/gpu/drm/i915/i915_suspend.c

@@ -240,6 +240,10 @@ int i915_save_state(struct drm_device *dev)
 
 	pci_read_config_byte(dev->pdev, LBB, &dev_priv->saveLBB);
 
+	/* Render Standby */
+	if (IS_I965G(dev) && IS_MOBILE(dev))
+		dev_priv->saveRENDERSTANDBY = I915_READ(MCHBAR_RENDER_STANDBY);
+
 	/* Display arbitration control */
 	dev_priv->saveDSPARB = I915_READ(DSPARB);
 
@@ -365,6 +369,11 @@ int i915_restore_state(struct drm_device *dev)
 
 	pci_write_config_byte(dev->pdev, LBB, dev_priv->saveLBB);
 
+	/* Render Standby */
+	if (IS_I965G(dev) && IS_MOBILE(dev))
+		I915_WRITE(MCHBAR_RENDER_STANDBY, dev_priv->saveRENDERSTANDBY);
+
+	/* Display arbitration */
 	I915_WRITE(DSPARB, dev_priv->saveDSPARB);
 
 	/* Pipe & plane A info */