[ 3.5.y.z extended stable ] Patch "drm/i915: do not disable backlight on vgaswitcheroo switch" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    drm/i915: do not disable backlight on vgaswitcheroo switch

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 605d7815de0a1e6d32f94026648a82d61f30e68c Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula at intel.com>
Date: Thu, 25 Jul 2013 14:31:30 +0300
Subject: [PATCH] drm/i915: do not disable backlight on vgaswitcheroo switch
 off

commit 3f577573cd5482a32f85bd131e52f7cb4b9ac518 upstream.

On muxed systems, the other vgaswitcheroo client may depend on i915 to
handle the backlight. We began switching off the backlight since

commit a261b246ebd552fd5d5a8ed84cc931bb821c427f
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Jul 26 19:21:47 2012 +0200

    drm/i915: disable all crtcs at suspend time

breaking backlight on discreet graphics in (some) muxed systems.

Keep the backlight on when the state is changed through vgaswitcheroo.

Note: The alternative would be to add a quirk table to achieve the same
based on system identifiers, but AFAICS it would asymptotically approach
effectively the same as this patch as more IDs are added, but with the
maintenance burden of the quirk table.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=55311
Tested-by: Fede <fedevx at yahoo.com>
Tested-by: Aximab <laurent.debian at gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=59785
Tested-by: sfievet <sebastien.fievet at free.fr>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/i915/intel_panel.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index d5fd67e..192002f 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -285,6 +285,17 @@ 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);
 }
--
1.8.3.2