Stable version 2.6.32.2 broke my KMS Radeon setup

[Ruud Linders]

Hello,

After upgrading from 2.6.32.1 to 2.6.32.2 my radeon KMS broke. Broke
meaning after kernel boot at the moment radeon module is loaded, I get a
blank screen, monitor goes in powersave mode and machine stops booting
(ping-able but can't login via ssh and nothing in the logs after
Sysrq-S-U-B reboot).

Upgraded userspace  (drm/mesa/xf86-video-ati) to git version from
19-december but no change.

Note this happens on 2 different systems, both connected via DVI-D to an
LCD monitor:
  Chipset: "ATI RV730XT [Radeon HD 4670]" (ChipID = 0x9490)
and
  Chipset: "ATI Radeon HD 3200 Graphics" (ChipID = 0x9610)

So I started looking at the diff between 2.6.32.1 & 2.6.32.2, backing
out attached change makes everything work again. Anything else I can
provide to debug/fix this, let me know.

Ruud

--- atombios_crtc.c	2009-12-20 12:28:42.921933107 +0100
+++ atombios_crtc.c.NEW	2009-12-20 12:28:36.223818764 +0100
@@ -241,6 +241,7 @@
 {
 	struct drm_device *dev = crtc->dev;
 	struct radeon_device *rdev = dev->dev_private;
+	struct radeon_crtc *radeon_crtc = to_radeon_crtc(crtc);
 
 	switch (mode) {
 	case DRM_MODE_DPMS_ON:
@@ -248,20 +249,19 @@
 		if (ASIC_IS_DCE3(rdev))
 			atombios_enable_crtc_memreq(crtc, 1);
 		atombios_blank_crtc(crtc, 0);
+		drm_vblank_post_modeset(dev, radeon_crtc->crtc_id);
+		radeon_crtc_load_lut(crtc);
 		break;
 	case DRM_MODE_DPMS_STANDBY:
 	case DRM_MODE_DPMS_SUSPEND:
 	case DRM_MODE_DPMS_OFF:
+		drm_vblank_pre_modeset(dev, radeon_crtc->crtc_id);
 		atombios_blank_crtc(crtc, 1);
 		if (ASIC_IS_DCE3(rdev))
 			atombios_enable_crtc_memreq(crtc, 0);
 		atombios_enable_crtc(crtc, 0);
 		break;
 	}
-
-	if (mode != DRM_MODE_DPMS_OFF) {
-		radeon_crtc_load_lut(crtc);
-	}
 }
 
 static void