3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Krzysztof Mazur <[email protected]>

commit 0fde901f1ddd2ce0e380a6444f1fb7ca555859e9 upstream.

Some broken systems (like HP nc6120) in some cases, usually after LID
close/open, enable VGA plane, making display unusable (black screen on LVDS,
some strange mode on VGA output). We used to disable VGA plane only once at
startup. Now we also check, if VGA plane is still disabled while changing
mode, and fix that if something changed it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=57434
Signed-off-by: Krzysztof Mazur <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
[bwh: Backported to 3.2: intel_modeset_setup_hw_state() does not
 exist, so call i915_redisable_vga() directly from intel_lid_notify()]
Signed-off-by: Ben Hutchings <[email protected]>
Cc: Qiang Huang <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/gpu/drm/i915/i915_drv.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |   17 +++++++++++++++++
 drivers/gpu/drm/i915/intel_lvds.c    |    1 +
 3 files changed, 19 insertions(+)

--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1397,6 +1397,7 @@ static inline void intel_unregister_dsm_
 #endif /* CONFIG_ACPI */
 
 /* modesetting */
+extern void i915_redisable_vga(struct drm_device *dev);
 extern void intel_modeset_init(struct drm_device *dev);
 extern void intel_modeset_gem_init(struct drm_device *dev);
 extern void intel_modeset_cleanup(struct drm_device *dev);
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9254,6 +9254,23 @@ static void i915_disable_vga(struct drm_
        POSTING_READ(vga_reg);
 }
 
+void i915_redisable_vga(struct drm_device *dev)
+{
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       u32 vga_reg;
+
+       if (HAS_PCH_SPLIT(dev))
+               vga_reg = CPU_VGACNTRL;
+       else
+               vga_reg = VGACNTRL;
+
+       if (I915_READ(vga_reg) != VGA_DISP_DISABLE) {
+               DRM_DEBUG_KMS("Something enabled VGA plane, disabling it\n");
+               I915_WRITE(vga_reg, VGA_DISP_DISABLE);
+               POSTING_READ(vga_reg);
+       }
+}
+
 void intel_modeset_init(struct drm_device *dev)
 {
        struct drm_i915_private *dev_priv = dev->dev_private;
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -535,6 +535,7 @@ static int intel_lid_notify(struct notif
 
        mutex_lock(&dev->mode_config.mutex);
        drm_helper_resume_force_mode(dev);
+       i915_redisable_vga(dev);
        mutex_unlock(&dev->mode_config.mutex);
 
        return NOTIFY_OK;


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