[Bug 55311] Since 3.7.1-17.1 radeon has no backlight when using vgaswitcheroo (regression)

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=55311

--- Comment #52 from Fede <fedevx at yahoo.com> ---
Hi Jani,

I had to adjust your patch to my current kernel source
(3.10.3-19.gec6c1d9-desktop). The lines you mentioned were not exactly at the
same location. Anyway, after applying the patch, the screen still goes black
while trying to do the switch.

The patch I tried earlier, was doing the check on intel_lvds.c instead in this
way:

!       if (INTEL_INFO(dev)->gen < 4) {
!               intel_panel_disable_backlight(dev);
!       }

Which seemed to work, at least for me. What is the difference between setting
the conditional in intel_lvds.c or intel_panel.c ?

By the way, I can't change the status of this ticket so it remains as NEEDINFO.

Here below is a copy of my version of your patch, just in case you want to make
sure I did not accidentally screwed it up.

*** ./a/intel_panel.c     2013-07-29 06:04:22.000000000 +0800
--- ./b/intel_panel.c    2013-07-29 06:10:32.000000000 +0800
***************
*** 299,305 ****
      struct drm_i915_private *dev_priv = dev->dev_private;

      dev_priv->backlight.enabled = false;
-     intel_panel_actually_set_backlight(dev, 0);

      if (INTEL_INFO(dev)->gen >= 4) {
          uint32_t reg, tmp;
--- 299,304 ----
***************
*** 313,318 ****
--- 312,321 ----
              tmp &= ~BLM_PCH_PWM_ENABLE;
              I915_WRITE(BLC_PWM_PCH_CTL1, tmp);
          }
+     } else {
+         /* pre-gen4 doesn't have a separate enable bit so we need to
+          * smash the actual backlight pwm to 0 */
+         intel_panel_actually_set_backlight(dev, 0);
      }
  }

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