Linux 2.6.39-rc5

[Takashi Iwai]

At Fri, 29 Apr 2011 17:58:06 +0200,
Melchior FRANZ wrote:
> 
> * Linus Torvalds -- Wednesday 27 April 2011:
> > Go forth and test,
> 
> Doesn't work on my notebook with i915/KMS. But then again, neither did
> 2.6.38 or any of its stable releases. The last working version was
> 2.6.38-rc8. The problem has been reported[1], but the bug got closed
> in the wrong assumption that the bug is fixed. I reported that, too.
> No reactions to that.
> 
> The bug was introduced with commit ba3820ade317ee36e496b9b40d2ec3987dd4aef0
> by Takashi Iwai. The result is that when using KMS my notebook's[2] screen
> remains dark, because the backlight isn't turned on.
> 
> Reverting commit ba3820ade317ee36e496b9b40d2ec3987dd4aef0 makes my
> notebook work correctly again as it used to in 2.6.38-rc8 and before.

Could you check whether the patch below changes the behavior?
If this cures, it means that the backlight-combo mode doesn't work on
your machine.


Takashi

---
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index a06ff07..bf61e02 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -116,11 +116,13 @@ static int is_backlight_combination_mode(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+#if 0
 	if (INTEL_INFO(dev)->gen >= 4)
 		return I915_READ(BLC_PWM_CTL2) & BLM_COMBINATION_MODE;
 
 	if (IS_GEN2(dev))
 		return I915_READ(BLC_PWM_CTL) & BLM_LEGACY_MODE;
+#endif
 
 	return 0;
 }