drm/i915: Fix OGLC performance regression on 945

He Shuang reported an OGLC performance regression introduced in the patch
"enable memory self refresh on 9xx", In that patch, SR on 945 is disabled
everytime when calling intel_mark_busy(), while too much of such operation
will impact performance. Actually disable SR is necessary only when GPU and
Crtc changing from idle to busy. This patch make such optimization.

It fixes upstream bug
http://bugs.freedesktop.org/show_bug.cgi?id=26422

Signed-off-by: Li Peng <peng.li@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_display.c

@@ -4060,18 +4060,17 @@ void intel_mark_busy(struct drm_device *dev, struct drm_gem_object *obj)
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return;
 
-	if (IS_I945G(dev) || IS_I945GM(dev)) {
-		u32 fw_blc_self;
-
-		DRM_DEBUG_DRIVER("disable memory self refresh on 945\n");
-		fw_blc_self = I915_READ(FW_BLC_SELF);
-		fw_blc_self &= ~FW_BLC_SELF_EN;
-		I915_WRITE(FW_BLC_SELF, fw_blc_self | FW_BLC_SELF_EN_MASK);
-	}
+	if (!dev_priv->busy) {
+		if (IS_I945G(dev) || IS_I945GM(dev)) {
+			u32 fw_blc_self;
 
-	if (!dev_priv->busy)
+			DRM_DEBUG_DRIVER("disable memory self refresh on 945\n");
+			fw_blc_self = I915_READ(FW_BLC_SELF);
+			fw_blc_self &= ~FW_BLC_SELF_EN;
+			I915_WRITE(FW_BLC_SELF, fw_blc_self | FW_BLC_SELF_EN_MASK);
+		}
 		dev_priv->busy = true;
-	else
+	} else
 		mod_timer(&dev_priv->idle_timer, jiffies +
 			  msecs_to_jiffies(GPU_IDLE_TIMEOUT));
 
@@ -4083,6 +4082,14 @@ void intel_mark_busy(struct drm_device *dev, struct drm_gem_object *obj)
 		intel_fb = to_intel_framebuffer(crtc->fb);
 		if (intel_fb->obj == obj) {
 			if (!intel_crtc->busy) {
+				if (IS_I945G(dev) || IS_I945GM(dev)) {
+					u32 fw_blc_self;
+
+					DRM_DEBUG_DRIVER("disable memory self refresh on 945\n");
+					fw_blc_self = I915_READ(FW_BLC_SELF);
+					fw_blc_self &= ~FW_BLC_SELF_EN;
+					I915_WRITE(FW_BLC_SELF, fw_blc_self | FW_BLC_SELF_EN_MASK);
+				}
 				/* Non-busy -> busy, upclock */
 				intel_increase_pllclock(crtc, true);
 				intel_crtc->busy = true;