drm/i915: don't access FW_BLC_SELF on 965G

The register offset for FW_BLC_SELF is a totally different set of bits
on Broadwater (it's actually MI_RDRET_STATE), so don't treat it like
FW_BLC_SELF on 965G chips.

Fixes bug https://bugs.freedesktop.org/show_bug.cgi?id=26874.

Cc: stable@kernel.org
Tested-by: Norman Yarvin <yarvin@yarchive.net>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6db778a..3acb766 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2970,11 +2970,13 @@
 		if (srwm < 0)
 			srwm = 1;
 		srwm &= 0x3f;
-		I915_WRITE(FW_BLC_SELF, FW_BLC_SELF_EN);
+		if (IS_I965GM(dev))
+			I915_WRITE(FW_BLC_SELF, FW_BLC_SELF_EN);
 	} else {
 		/* Turn off self refresh if both pipes are enabled */
-		I915_WRITE(FW_BLC_SELF, I915_READ(FW_BLC_SELF)
-					& ~FW_BLC_SELF_EN);
+		if (IS_I965GM(dev))
+			I915_WRITE(FW_BLC_SELF, I915_READ(FW_BLC_SELF)
+				   & ~FW_BLC_SELF_EN);
 	}
 
 	DRM_DEBUG_KMS("Setting FIFO watermarks - A: 8, B: 8, C: 8, SR %d\n",