[Intel-gfx] [PATCH] drm/i915: Fix eDP blank screen after S3 resume on HP desktops

[Takashi Iwai]

This patch fixes the problem on some HP desktop machines with eDP
which give blank screens after S3 resume.

The problem looks like a timing issue.  Although BLC_PWM_CPU_CTL
register is already restored at the beginning of resume, it doesn't
seem to take effect.  Simply re-issuing the  register write restores
the backlight gracefully.

Tested with 3.5-rc3 kernel.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49233

Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 drivers/gpu/drm/i915/i915_drv.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 9fe9ebe..2ba1350 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -658,6 +658,9 @@ static int i915_drm_thaw(struct drm_device *dev)
 
 	intel_opregion_init(dev);
 
+	if (dev_priv->backlight)
+		backlight_update_status(dev_priv->backlight);
+
 	dev_priv->modeset_on_lid = 0;
 
 	console_lock();
-- 
1.7.10.4