[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 #53 from Jani Nikula <jani.nikula at intel.com> ---
Fede, I think you've used the wrong patch as the starting point. I'm checking
for dev->switch_power_state == DRM_SWITCH_POWER_CHANGING, *not* the gen. Please
try again with the attachment titled "drm/i915: do not disable backlight on
vgaswitcheroo switch off".

This is what it should look like on 3.10, although I'd obviously prefer you
tried the latest 3.11-rc.

diff --git a/drivers/gpu/drm/i915/intel_panel.c
b/drivers/gpu/drm/i915/intel_panel.c
index eb5e6e9..9275169 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -298,6 +298,17 @@ void intel_panel_disable_backlight(struct drm_device *dev)
 {
     struct drm_i915_private *dev_priv = dev->dev_private;

+    /*
+     * Do not disable backlight on the vgaswitcheroo path. When switching
+     * away from i915, the other client may depend on i915 to handle the
+     * backlight. This will leave the backlight on unnecessarily when
+     * another client is not activated.
+     */
+    if (dev->switch_power_state == DRM_SWITCH_POWER_CHANGING) {
+        DRM_DEBUG_DRIVER("Skipping backlight disable on vga switch\n");
+        return;
+    }
+
     dev_priv->backlight.enabled = false;
     intel_panel_actually_set_backlight(dev, 0);

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