Re: 2.6.32 regression (bisected): Video tearing/glitching with T400 laptops

[Arkadiusz Miskiewicz <a.miskiewicz@gmail.com>]

On Saturday 03 of October 2009, Theodore Ts'o wrote:
> Hi,
> 
> In recent kernels, my X display (running with a KMS-enabled X server)
> has been very jittery and with lots of glitching and tearing --- sorry
> if this isn't the correct technical term, not sure what it is --- on my
> T400 Lenovo laptop.   It seems related to what is on the desktop, and
> moving the mouse does seem to affect the rate and percentage of the
> screen which jitters --- which is enough to be very distracting,
> although I can still read the contents of the windows where the screen
> is tearing/glitching/flashing.
> 
> I bisected it down to this commit:
> 
> 74dff282237ea8c0a5df1afd8526eac4b6cee063 is the first bad commit
> commit 74dff282237ea8c0a5df1afd8526eac4b6cee063
> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
> Date:   Mon Sep 14 15:39:40 2009 -0700
> 
>     drm/i915: framebuffer compression for GM45+

Disabling compression works fine (as temporary workaround until the issue is 
solved).

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 7a5fb79..075092b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4165,7 +4165,7 @@ static void intel_init_display(struct drm_device *dev)
 
 	/* Only mobile has FBC, leave pointers NULL for other chips */
 	if (IS_MOBILE(dev)) {
-		if (IS_GM45(dev)) {
+		if (0 && IS_GM45(dev)) {
 			dev_priv->display.fbc_enabled = g4x_fbc_enabled;
 			dev_priv->display.enable_fbc = g4x_enable_fbc;
 			dev_priv->display.disable_fbc = g4x_disable_fbc;


-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/